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1
Vervoort, Michel, e Valerie Ledent. "The Evolution of the Neural Basic Helix-Loop-Helix Proteins". Scientific World JOURNAL 1 (2001): 396–426. http://dx.doi.org/10.1100/tsw.2001.68.
Testo completoAbstract (sommario):
Basic Helix-Loop-Helix (bHLH) transcription factors control various aspects of the formation of the nervous system in the metazoans. In Drosophila some bHLH (such as the achaete-scuteatonal, and amos genes) act as proneural genes, directing ectodermal cells toward a neural fate. Their vertebrate orthologs, however, probably do not assume such a neural determination function, but rather control the decision made by neural precursors to generate neurons and not glial cells, as well as the progression of neuronal precursors toward differentiation into mature neurons. The proneural function of Drosophila bHLH genes may be an innovation that occurs in the evolutive lineage that leads to arthropods. In addition, although neural bHLH appear to be involved in the specification of neuronal identities, they probably do not confer by themselves neuronal type-specific properties to the cells. Rather, neural bHLH allow neural cells to correctly interpret specification and positional cues provided by other factors. Although bHLH genes are often expressed in complementary subsets of neural cells and/or expressed sequentially in those cells, the coding regions of the various neural bHLH appear largely interchangeable. We propose that the specific expression patterns have been acquired, following gene duplications, by subfunctional-ization, i.e., the partitioning of ancestral expression patterns among the duplicates and, by extension, we propose that subfunctionalization is a key process to understand the evolution of neural bHLH genes.
2
Hudson, Karen A., e Matthew E. Hudson. "A Classification of Basic Helix-Loop-Helix Transcription Factors of Soybean". International Journal of Genomics 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/603182.
Testo completoAbstract (sommario):
The complete genome sequence of soybean allows an unprecedented opportunity for the discovery of the genes controlling important traits. In particular, the potential functions of regulatory genes are a priority for analysis. The basic helix-loop-helix (bHLH) family of transcription factors is known to be involved in controlling a wide range of systems critical for crop adaptation and quality, including photosynthesis, light signalling, pigment biosynthesis, and seed pod development. Using a hidden Markov model search algorithm, 319 genes with basic helix-loop-helix transcription factor domains were identified within the soybean genome sequence. These were classified with respect to their predicted DNA binding potential, intron/exon structure, and the phylogeny of the bHLH domain. Evidence is presented that the vast majority (281) of these 319 soybean bHLH genes are expressed at the mRNA level. Of these soybean bHLH genes, 67% were found to exist in two or more homeologous copies. This dataset provides a framework for future studies on bHLH gene function in soybean. The challenge for future research remains to define functions for the bHLH factors encoded in the soybean genome, which may allow greater flexibility for genetic selection of growth and environmental adaptation in this widely grown crop.
3
Funato, Noriko. "Basic Helix-Loop-Helix (bHLH) Factors in Osteoblast Differentiation". Journal of Oral Biosciences 46, n. 3 (giugno 2004): 191–202. http://dx.doi.org/10.1016/s1349-0079(04)80002-1.
Testo completo
4
Torres-Machorro, Ana Lilia. "Homodimeric and Heterodimeric Interactions among Vertebrate Basic Helix–Loop–Helix Transcription Factors". International Journal of Molecular Sciences 22, n. 23 (28 novembre 2021): 12855. http://dx.doi.org/10.3390/ijms222312855.
Testo completoAbstract (sommario):
The basic helix–loop–helix transcription factor (bHLH TF) family is involved in tissue development, cell differentiation, and disease. These factors have transcriptionally positive, negative, and inactive functions by combining dimeric interactions among family members. The best known bHLH TFs are the E-protein homodimers and heterodimers with the tissue-specific TFs or ID proteins. These cooperative and dynamic interactions result in a complex transcriptional network that helps define the cell’s fate. Here, the reported dimeric interactions of 67 vertebrate bHLH TFs with other family members are summarized in tables, including specifications of the experimental techniques that defined the dimers. The compilation of these extensive data underscores homodimers of tissue-specific bHLH TFs as a central part of the bHLH regulatory network, with relevant positive and negative transcriptional regulatory roles. Furthermore, some sequence-specific TFs can also form transcriptionally inactive heterodimers with each other. The function, classification, and developmental role for all vertebrate bHLH TFs in four major classes are detailed.
5
Liu, Wu-yi, e Chun-jiang Zhao. "Genome-Wide Identification and Analysis of the Chicken Basic Helix-Loop-Helix Factors". Comparative and Functional Genomics 2010 (2010): 1–12. http://dx.doi.org/10.1155/2010/682095.
Testo completoAbstract (sommario):
Members of the basic helix-loop-helix (bHLH) family of transcription factors play important roles in a wide range of developmental processes. In this study, we conducted a genome-wide survey using the chicken (Gallus gallus) genomic database, and identified 104 bHLH sequences belonging to 42 gene families in an effort to characterize the chicken bHLH transcription factor family. Phylogenetic analyses revealed that chicken has 50, 21, 15, 4, 8, and 3 bHLH members in groups A, B, C, D, E, and F, respectively, while three members belonging to none of these groups were classified as ‘‘orphans’’. A comparison between chicken and human bHLH repertoires suggested that both organisms have a number of lineage-specific bHLH members in the proteomes. Chromosome distribution patterns and phylogenetic analyses strongly suggest that the bHLH members should have arisen through gene duplication at an early date. Gene Ontology (GO) enrichment statistics showed 51 top GO annotations of biological processes counted in the frequency. The present study deepens our understanding of the chicken bHLH transcription factor family and provides much useful information for further studies using chicken as a model system.
6
Tian, Gang, Batu Erman, Haruhiko Ishii, Samudra S. Gangopadhyay e Ranjan Sen. "Transcriptional Activation by ETS and Leucine Zipper-Containing Basic Helix-Loop-Helix Proteins". Molecular and Cellular Biology 19, n. 4 (1 aprile 1999): 2946–57. http://dx.doi.org/10.1128/mcb.19.4.2946.
Testo completoAbstract (sommario):
ABSTRACT The immunoglobulin μ heavy-chain gene enhancer contains closely juxtaposed binding sites for ETS and leucine zipper-containing basic helix-loop-helix (bHLH-zip) proteins. To understand the μ enhancer function, we have investigated transcription activation by the combination of ETS and bHLH-zip proteins. The bHLH-zip protein TFE3, but not USF, cooperated with the ETS domain proteins PU.1 and Ets-1 to activate a tripartite domain of this enhancer. Deletion mutants were used to identify the domains of the proteins involved. Both TFE3 and USF enhanced Ets-1 DNA binding in vitro by relieving the influence of an autoinhibitory domain in Ets-1 by direct protein-protein associations. Several regions of Ets-1 were found to be necessary, whereas the bHLH-zip domain was sufficient for this effect. Our studies define novel interactions between ETS and bHLH-zip proteins that may regulate combinatorial transcription activation by these protein families.
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Hou, Quancan, Wei Zhao, Lu Lu, Linlin Wang, Tianye Zhang, Binbin Hu, Tingwei Yan et al. "Overexpression of HLH4 Inhibits Cell Elongation and Anthocyanin Biosynthesis in Arabidopsis thaliana". Cells 11, n. 7 (24 marzo 2022): 1087. http://dx.doi.org/10.3390/cells11071087.
Testo completoAbstract (sommario):
In plants, many basic helix-loop-helix (bHLH) transcription factors are involved in controlling cell elongation. Three bHLH proteins, PACLOBTRAZOL RESISTANCE1 (PRE1), Cryptochrome Interacting Basic Helix-loop-helix 5 (CIB5), and Arabidopsis ILI1 binding bHLH1 (IBH1) form a triantagonistic system that antagonistically regulates cell elongation in a competitive manner. In this study, we identified a new player, HLH4, related to IBH1, that negatively regulates cell elongation in Arabidopsis thaliana. Overexpression of HLH4 causes dwarf and dark green phenotypes and results in the downregulation of many key regulatory and enzymatic genes that participate in the anthocyanin biosynthetic pathway. HLH4 interacts with CIB5 and PRE1. By interacting with CIB5, HLH4 interferes with the activity of CIB5, and thus inhibiting the transcription of cell elongation-related genes regulated by CIB5, including EXPANSINS8 and 11 (EXP8 and EXP11) and indole-3-acetic acid 7 and 17 (IAA7 and IAA17). The interference of HLH4 on CIB5 is counteracted by PRE1, in which these bHLH proteins form a new tri-antagonistic system.
8
Zuo, Zhi-Fang, Hyo-Yeon Lee e Hong-Gyu Kang. "Basic Helix-Loop-Helix Transcription Factors: Regulators for Plant Growth Development and Abiotic Stress Responses". International Journal of Molecular Sciences 24, n. 2 (11 gennaio 2023): 1419. http://dx.doi.org/10.3390/ijms24021419.
Testo completoAbstract (sommario):
Plant basic helix-loop-helix (bHLH) transcription factors are involved in many physiological processes, and they play important roles in the abiotic stress responses. The literature related to genome sequences has increased, with genome-wide studies on the bHLH transcription factors in plants. Researchers have detailed the functionally characterized bHLH transcription factors from different aspects in the model plant Arabidopsis thaliana, such as iron homeostasis and abiotic stresses; however, other important economic crops, such as rice, have not been summarized and highlighted. The bHLH members in the same subfamily have similar functions; therefore, unraveling their regulatory mechanisms will help us to identify and understand the roles of some of the unknown bHLH transcription factors in the same subfamily. In this review, we summarize the available knowledge on functionally characterized bHLH transcription factors according to four categories: plant growth and development; metabolism synthesis; plant signaling, and abiotic stress responses. We also highlight the roles of the bHLH transcription factors in some economic crops, especially in rice, and discuss future research directions for possible genetic applications in crop breeding.
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Chen, Meng, e John M. Lopes. "Multiple Basic Helix-Loop-Helix Proteins Regulate Expression of the ENO1 Gene of Saccharomyces cerevisiae". Eukaryotic Cell 6, n. 5 (9 marzo 2007): 786–96. http://dx.doi.org/10.1128/ec.00383-06.
Testo completoAbstract (sommario):
ABSTRACT The basic helix-loop-helix (bHLH) eukaryotic transcription factors have the ability to form multiple dimer combinations. This property, together with limited DNA-binding specificity for the E box (CANNTG), makes them ideally suited for combinatorial control of gene expression. We tested the ability of all nine Saccharomyces cerevisiae bHLH proteins to regulate the enolase-encoding gene ENO1. ENO1 was known to be activated by the bHLH protein Sgc1p. Here we show that expression of an ENO1-lacZ reporter was also regulated by the other eight bHLH proteins, namely, Ino2p, Ino4p, Cbf1p, Rtg1p, Rtg3p, Pho4p, Hms1p, and Ygr290wp. ENO1-lacZ expression was also repressed by growth in inositol-choline-containing medium. Epistatic analysis and chromatin immunoprecipitation experiments showed that regulation by Sgc1p, Ino2p, Ino4p, and Cbf1p and repression by inositol-choline required three distal E boxes, E1, E2, and E3. The pattern of bHLH binding to the three E boxes and experiments with two dominant-negative mutant alleles of INO4 and INO2 support the model that bHLH dimer selection affects ENO1-lacZ expression. These results support the general model that bHLH proteins can coordinate different biological pathways via multiple mechanisms.
10
Chen, Yu, Peihuang Zhu, Fan Wu, Xiaofeng Wang, Jinfeng Zhang e Kongshu Ji. "Identification and Characterization of the Basic Helix-Loop-Helix Transcription Factor Family in Pinus massoniana". Forests 11, n. 12 (30 novembre 2020): 1292. http://dx.doi.org/10.3390/f11121292.
Testo completoAbstract (sommario):
The basic helix-loop-helix (bHLH) protein transcription factor family is the most widely distributed transcription factor family in eukaryotes. Members of this family play important roles in secondary metabolic biosynthesis, signal transduction, and plant resistance. Research on the bHLH family in animals is more extensive than that in plants, and members of the family in plants are classified according to the classification criteria for those in animals. To date, no research on the bHLH gene family in Pinus massoniana (Masson pine) has been reported. In this study, we identified 88 bHLH genes from four transcriptomes of Masson pine and performed bioinformatics analysis. These genes were divided into 10 groups in total. RT-PCR analysis revealed that the expression levels of the six genes increased under abiotic stress and hormone treatments. These findings will facilitate further studies on the functions of bHLH transcription factors.
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Cserjesi, P., D. Brown, K. L. Ligon, G. E. Lyons, N. G. Copeland, D. J. Gilbert, N. A. Jenkins e E. N. Olson. "Scleraxis: a basic helix-loop-helix protein that prefigures skeletal formation during mouse embryogenesis". Development 121, n. 4 (1 aprile 1995): 1099–110. http://dx.doi.org/10.1242/dev.121.4.1099.
Testo completoAbstract (sommario):
Members of the basic helix-loop-helix (bHLH) family of transcription factors have been shown to regulate growth and differentiation of numerous cell types. Cell-type-specific bHLH proteins typically form heterodimers with ubiquitous bHLH proteins, such as E12, and bind a DNA consensus sequence known as an E-box. We used the yeast two-hybrid system to screen mouse embryo cDNA libraries for cDNAs encoding novel cell-type-specific bHLH proteins that dimerize with E12. One of the cDNAs isolated encoded a novel bHLH protein, called scleraxis. During mouse embryogenesis, scleraxis transcripts were first detected between day 9.5 and 10.5 post coitum (p.c.) in the sclerotome of the somites and in mesenchymal cells in the body wall and limb buds. Subsequently, scleraxis was expressed at high levels within mesenchymal precursors of the axial and appendicular skeleton and in cranial mesenchyme in advance of chondrogenesis; its expression pattern in these cell types foreshadowed the developing skeleton. Prior to formation of the embryonic cartilaginous skeleton, scleraxis expression declined to low levels. As development proceeded, high levels of scleraxis expression became restricted to regions where cartilage and connective tissue formation take place. Scleraxis bound the E-box consensus sequence as a heterodimer with E12 and activated transcription of a reporter gene linked to its DNA-binding site. The expression pattern, DNA-binding properties and transcriptional activity of scleraxis suggest that it is a regulator of gene expression within mesenchymal cell lineages that give rise to cartilage and connective tissue.
12
Bergstrom, Donald A., e Stephen J. Tapscott. "Molecular Distinction between Specification and Differentiation in the Myogenic Basic Helix-Loop-Helix Transcription Factor Family". Molecular and Cellular Biology 21, n. 7 (1 aprile 2001): 2404–12. http://dx.doi.org/10.1128/mcb.21.7.2404-2412.2001.
Testo completoAbstract (sommario):
ABSTRACT The myogenic basic helix-loop-helix (bHLH) proteins regulate both skeletal muscle specification and differentiation: MyoD and Myf5 establish the muscle lineage, whereas myogenin mediates differentiation. Previously, we demonstrated that MyoD was more efficient than myogenin at initiating the expression of skeletal muscle genes, and in this study we present the molecular basis for this difference. A conserved amphipathic alpha-helix in the carboxy terminus of the myogenic bHLH proteins has distinct activities in MyoD and myogenin: the MyoD helix facilitates the initiation of endogenous gene expression, whereas the myogenin helix functions as a general transcriptional activation domain. Thus, the alternate use of a similar motif for gene initiation and activation provides a molecular basis for the distinction between specification and differentiation within the myogenic bHLH gene family.
13
Hao, Yaqi, Xiumei Zong, Pan Ren, Yuqi Qian e Aigen Fu. "Basic Helix-Loop-Helix (bHLH) Transcription Factors Regulate a Wide Range of Functions in Arabidopsis". International Journal of Molecular Sciences 22, n. 13 (1 luglio 2021): 7152. http://dx.doi.org/10.3390/ijms22137152.
Testo completoAbstract (sommario):
The basic helix-loop-helix (bHLH) transcription factor family is one of the largest transcription factor gene families in Arabidopsis thaliana, and contains a bHLH motif that is highly conserved throughout eukaryotic organisms. Members of this family have two conserved motifs, a basic DNA binding region and a helix-loop-helix (HLH) region. These proteins containing bHLH domain usually act as homo- or heterodimers to regulate the expression of their target genes, which are involved in many physiological processes and have a broad range of functions in biosynthesis, metabolism and transduction of plant hormones. Although there are a number of articles on different aspects to provide detailed information on this family in plants, an overall summary is not available. In this review, we summarize various aspects of related studies that provide an overview of insights into the pleiotropic regulatory roles of these transcription factors in plant growth and development, stress response, biochemical functions and the web of signaling networks. We then provide an overview of the functional profile of the bHLH family and the regulatory mechanisms of other proteins.
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Poulin, Gino, Mélanie Lebel, Michel Chamberland, Francois W. Paradis e Jacques Drouin. "Specific Protein-Protein Interaction between Basic Helix-Loop-Helix Transcription Factors and Homeoproteins of the Pitx Family". Molecular and Cellular Biology 20, n. 13 (1 luglio 2000): 4826–37. http://dx.doi.org/10.1128/mcb.20.13.4826-4837.2000.
Testo completoAbstract (sommario):
ABSTRACT Homeoproteins and basic helix-loop-helix (bHLH) transcription factors are known for their critical role in development and cellular differentiation. The pituitary pro-opiomelanocortin (POMC) gene is a target for factors of both families. Indeed, pituitary-specific transcription of POMC depends on the action of the homeodomain-containing transcription factor Pitx1 and of bHLH heterodimers containing NeuroD1. We now show lineage-restricted expression of NeuroD1 in pituitary corticotroph cells and a direct physical interaction between bHLH heterodimers and Pitx1 that results in transcriptional synergism. The interaction between the bHLH and homeodomains is restricted to ubiquitous (class A) bHLH and to the Pitx subfamily. Since bHLH heterodimers interact with Pitx factors through their ubiquitous moiety, this mechanism may be implicated in other developmental processes involving bHLH factors, such as neurogenesis and myogenesis.
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Vojtek, Anne B., Jennifer Taylor, Stacy L. DeRuiter, Jenn-Yah Yu, Claudia Figueroa, Roland P. S. Kwok e David L. Turner. "Akt Regulates Basic Helix-Loop-Helix Transcription Factor-Coactivator Complex Formation and Activity during Neuronal Differentiation". Molecular and Cellular Biology 23, n. 13 (1 luglio 2003): 4417–27. http://dx.doi.org/10.1128/mcb.23.13.4417-4427.2003.
Testo completoAbstract (sommario):
ABSTRACT Neural basic helix-loop-helix (bHLH) transcription factors regulate neurogenesis in vertebrates. Signaling by peptide growth factors also plays critical roles in regulating neuronal differentiation and survival. Many peptide growth factors activate phosphatidylinositol 3-kinase (PI3K) and subsequently the Akt kinases, raising the possibility that Akt may impact bHLH protein function during neurogenesis. Here we demonstrate that reducing expression of endogenous Akt1 and Akt2 by RNA interference (RNAi) reduces neuron generation in P19 cells transfected with a neural bHLH expression vector. The reduction in neuron generation from decreased Akt expression is not solely due to decreased cell survival, since addition of the caspase inhibitor z-VAD-FMK rescues cell death associated with loss of Akt function but does not restore neuron formation. This result indicates that Akt1 and Akt2 have additional functions during neuronal differentiation that are separable from neuronal survival. We show that activated Akt1 enhances complex formation between bHLH proteins and the transcriptional coactivator p300. Activated Akt1 also significantly augments the transcriptional activity of the bHLH protein neurogenin 3 in complex with the coactivators p300 or CBP. In addition, inhibition of endogenous Akt activity by the PI3K/Akt inhibitor LY294002 abolishes transcriptional cooperativity between the bHLH proteins and p300. We propose that Akt regulates the assembly and activity of bHLH-coactivator complexes to promote neuronal differentiation.
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Dang, Wei, Xiao-hong Sun e Ranjan Sen. "ETS-Mediated Cooperation between Basic Helix-Loop-Helix Motifs of the Immunoglobulin μ Heavy-Chain Gene Enhancer". Molecular and Cellular Biology 18, n. 3 (1 marzo 1998): 1477–88. http://dx.doi.org/10.1128/mcb.18.3.1477.
Testo completoAbstract (sommario):
ABSTRACT The μE motifs of the immunoglobulin μ heavy-chain gene enhancer bind ubiquitously expressed proteins of the basic helix-loop-helix (bHLH) family. These elements work together with other, more tissue-restricted elements to produce B-cell-specific enhancer activity by presently undefined combinatorial mechanisms. We found that μE2 contributed to transcription activation in B cells only when the μE3 site was intact, providing the first evidence for functional interactions between bHLH proteins. In vitro assays showed that bHLH zipper proteins binding to μE3 enhanced Ets-1 binding to μA. One of the consequences of this protein-protein interaction was to facilitate binding of a second bHLH protein, E47, to the μE2 site, thereby generating a three-protein–DNA complex. Furthermore, transcriptional synergy between bHLH and bHLH zipper factors also required an intermediate ETS protein, which may bridge the transcription activation domains of the bHLH factors. Our observations define an unusual form of cooperation between bHLH and ETS proteins and suggest mechanisms by which tissue-restricted and ubiquitous factors combine to generate tissue-specific enhancer activity.
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Scott, Ian C., Lynn Anson-Cartwright, Paul Riley, Danny Reda e James C. Cross. "The HAND1 Basic Helix-Loop-Helix Transcription Factor Regulates Trophoblast Differentiation via Multiple Mechanisms". Molecular and Cellular Biology 20, n. 2 (15 gennaio 2000): 530–41. http://dx.doi.org/10.1128/mcb.20.2.530-541.2000.
Testo completoAbstract (sommario):
ABSTRACT The basic helix-loop-helix (bHLH) transcription factor genesHand1 and Mash2 are essential for placental development in mice. Hand1 promotes differentiation of trophoblast giant cells, whereas Mash2 is required for the maintenance of giant cell precursors, and its overexpression prevents giant cell differentiation. We found that Hand1 expression and Mash2 expression overlap in the ectoplacental cone and spongiotrophoblast, layers of the placenta that contain the giant cell precursors, indicating that the antagonistic activities ofHand1 and Mash2 must be coordinated. MASH2 and HAND1 both heterodimerize with E factors, bHLH proteins that are the DNA-binding partners for most class B bHLH factors and which are also expressed in the ectoplacental cone and spongiotrophoblast. In vitro, HAND1 could antagonize MASH2 function by competing for E-factor binding. However, the Hand1 mutant phenotype cannot be solely explained by ectopic activity of MASH2, as the Hand1mutant phenotype was not altered by further mutation ofMash2. Interestingly, expression of E-factor genes (ITF2 and ALF1) was down-regulated in the trophoblast lineage prior to giant cell differentiation. Therefore, suppression of MASH2 function, required to allow giant cell differentiation, may occur in vivo by loss of its E-factor partner due to loss of its expression and/or competition from HAND1. In giant cells, where E-factor expression was not detected, HAND1 presumably associates with a different bHLH partner. This may account for the distinct functions of HAND1 in giant cells and their precursors. We conclude that development of the trophoblast lineage is regulated by the interacting functions of HAND1, MASH2, and their cofactors.
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Guo, Jianrong, Baixue Sun, Huanrong He, Yifan Zhang, Huaying Tian e Baoshan Wang. "Current Understanding of bHLH Transcription Factors in Plant Abiotic Stress Tolerance". International Journal of Molecular Sciences 22, n. 9 (6 maggio 2021): 4921. http://dx.doi.org/10.3390/ijms22094921.
Testo completoAbstract (sommario):
Named for the characteristic basic helix-loop-helix (bHLH) region in their protein structure, bHLH proteins are a widespread transcription factor class in eukaryotes. bHLHs transcriptionally regulate their target genes by binding to specific positions on their promoters and thereby direct a variety of plant developmental and metabolic processes, such as photomorphogenesis, flowering induction, shade avoidance, and secondary metabolite biosynthesis, which are important for promoting plant tolerance or adaptation to adverse environments. In this review, we discuss the vital roles of bHLHs in plant responses to abiotic stresses, such as drought, salinity, cold, and iron deficiency. We suggest directions for future studies into the roles of bHLH genes in plant and discuss their potential applications in crop breeding.
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Wang, Zi Yuan, Yue Gao, Jingmiao Liu, Vikranth Kumar, Tian Ya Li e Yuan Hu Xuan. "Basic helix-loop-helix ( bHLH ) transcriptional activator regulates ammonium uptake in rice". Plant Gene 12 (dicembre 2017): 57–65. http://dx.doi.org/10.1016/j.plgene.2017.07.008.
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Mattar, Pierre, Lisa Marie Langevin, Kathryn Markham, Natalia Klenin, Salma Shivji, Dawn Zinyk e Carol Schuurmans. "Basic Helix-Loop-Helix Transcription Factors Cooperate To Specify a Cortical Projection Neuron Identity". Molecular and Cellular Biology 28, n. 5 (26 dicembre 2007): 1456–69. http://dx.doi.org/10.1128/mcb.01510-07.
Testo completoAbstract (sommario):
ABSTRACT Several transcription factors are essential determinants of a cortical projection neuron identity, but their mode of action (instructive versus permissive) and downstream genetic cascades remain poorly defined. Here, we demonstrate that the proneural basic helix-loop-helix (bHLH) gene Ngn2 instructs a partial cortical identity when misexpressed in ventral telencephalic progenitors, inducing ectopic marker expression in a defined temporal sequence, including early (24 h; Nscl2), intermediate (48 h; BhlhB5), and late (72 h; NeuroD, NeuroD2, Math2, and Tbr1) target genes. Strikingly, cortical gene expression was much more rapidly induced by Ngn2 in the dorsal telencephalon (within 12 to 24 h). We identify the bHLH gene Math3 as a dorsally restricted Ngn2 transcriptional target and cofactor, which synergizes with Ngn2 to accelerate target gene transcription in the cortex. Using a novel in vivo luciferase assay, we show that Ngn2 generates only ∼60% of the transcriptional drive in ventral versus dorsal telencephalic domains, an activity that is augmented by Math3, providing a mechanistic basis for regional differences in Ngn2 function. Cortical bHLH genes thus cooperate to control transcriptional strength, thereby temporally coordinating downstream gene expression.
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Inamoto, Ichiro, Gang Chen e Jumi A. Shin. "The DNA target determines the dimerization partner selected by bHLHZ-like hybrid proteins AhRJun and ArntFos". Molecular BioSystems 13, n. 3 (2017): 476–88. http://dx.doi.org/10.1039/c6mb00795c.
Testo completoAbstract (sommario):
The molecular basis of protein–partner selection and DNA binding of the basic helix–loop–helix (bHLH) and basic region-leucine zipper (bZIP) superfamilies of dimeric transcription factors is fundamental toward understanding gene regulation.
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McGuire, J., M. L. Whitelaw, I. Pongratz, J. A. Gustafsson e L. Poellinger. "A cellular factor stimulates ligand-dependent release of hsp90 from the basic helix-loop-helix dioxin receptor". Molecular and Cellular Biology 14, n. 4 (aprile 1994): 2438–46. http://dx.doi.org/10.1128/mcb.14.4.2438-2446.1994.
Testo completoAbstract (sommario):
In response to dioxin, the nuclear basic helix-loop-helix (bHLH) dioxin receptor forms a complex with the bHLH partner factor Arnt that regulates target gene transcription by binding to dioxin-responsive sequence motifs. Previously, we have demonstrated that the latent form of dioxin receptor present in extracts from untreated cells is stably associated with molecular chaperone protein hsp90, and Arnt is not a component of this complex. Here, we used a coimmunoprecipitation assay to demonstrate that the in vitro-translated dioxin receptor, but not Arnt, is stably associated with hsp90. Although it showed ligand-binding activity, the in vitro-translated dioxin receptor failed to dissociate from hsp90 upon exposure to ligand. Addition of a specific fraction from wild-type hepatoma cells, however, to the in vitro-expressed receptor promoted dioxin-dependent release of hsp90. This stimulatory effect was mediated via the bHLH dimerization and DNA-binding motif of the receptor. Moreover, ligand-dependent release of hsp90 from the receptor was not promoted by fractionated cytosolic extracts from mutant hepatoma cells which are deficient in the function of bHLH dioxin receptor partner factor Arnt. Thus, our results provide a novel model for regulation of bHLH factor activity and suggest that derepression of the dioxin receptor by ligand-induced release of hsp90 may require bHLH-mediated concomitant recruitment of an additional cellular factor, possibly the structurally related bHLH dimerization partner factor Arnt. In support of this model, addition of in vitro-expressed wild-type Arnt, but not a mutated form of Arnt lacking the bHLH motif, promoted release of hsp90 from the dioxin receptor in the presence of dioxin.
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McGuire, J., M. L. Whitelaw, I. Pongratz, J. A. Gustafsson e L. Poellinger. "A cellular factor stimulates ligand-dependent release of hsp90 from the basic helix-loop-helix dioxin receptor." Molecular and Cellular Biology 14, n. 4 (aprile 1994): 2438–46. http://dx.doi.org/10.1128/mcb.14.4.2438.
Testo completoAbstract (sommario):
In response to dioxin, the nuclear basic helix-loop-helix (bHLH) dioxin receptor forms a complex with the bHLH partner factor Arnt that regulates target gene transcription by binding to dioxin-responsive sequence motifs. Previously, we have demonstrated that the latent form of dioxin receptor present in extracts from untreated cells is stably associated with molecular chaperone protein hsp90, and Arnt is not a component of this complex. Here, we used a coimmunoprecipitation assay to demonstrate that the in vitro-translated dioxin receptor, but not Arnt, is stably associated with hsp90. Although it showed ligand-binding activity, the in vitro-translated dioxin receptor failed to dissociate from hsp90 upon exposure to ligand. Addition of a specific fraction from wild-type hepatoma cells, however, to the in vitro-expressed receptor promoted dioxin-dependent release of hsp90. This stimulatory effect was mediated via the bHLH dimerization and DNA-binding motif of the receptor. Moreover, ligand-dependent release of hsp90 from the receptor was not promoted by fractionated cytosolic extracts from mutant hepatoma cells which are deficient in the function of bHLH dioxin receptor partner factor Arnt. Thus, our results provide a novel model for regulation of bHLH factor activity and suggest that derepression of the dioxin receptor by ligand-induced release of hsp90 may require bHLH-mediated concomitant recruitment of an additional cellular factor, possibly the structurally related bHLH dimerization partner factor Arnt. In support of this model, addition of in vitro-expressed wild-type Arnt, but not a mutated form of Arnt lacking the bHLH motif, promoted release of hsp90 from the dioxin receptor in the presence of dioxin.
24
Hsu, H. L., L. Huang, J. T. Tsan, W. Funk, W. E. Wright, J. S. Hu, R. E. Kingston e R. Baer. "Preferred sequences for DNA recognition by the TAL1 helix-loop-helix proteins". Molecular and Cellular Biology 14, n. 2 (febbraio 1994): 1256–65. http://dx.doi.org/10.1128/mcb.14.2.1256-1265.1994.
Testo completoAbstract (sommario):
Tumor-specific activation of the TAL1 gene is the most common genetic alteration seen in patients with T-cell acute lymphoblastic leukemia. The TAL1 gene products contain the basic helix-loop-helix (bHLH) domain, a protein dimerization and DNA-binding motif common to several known transcription factors. A binding-site selection procedure has now been used to evaluate the DNA recognition properties of TAL1. These studies demonstrate that TAL1 polypeptides do not have intrinsic DNA-binding activity, presumably because of their inability to form bHLH homodimers. However, TAL1 readily interacts with any of the known class A bHLH proteins (E12, E47, E2-2, and HEB) to form heterodimers that bind DNA in a sequence-specific manner. The TAL1 heterodimers preferentially recognize a subset of E-box elements (CANNTG) that can be represented by the consensus sequence AACAGATGGT. This consensus is composed of half-sites for recognition by the participating class A bHLH polypeptide (AACAG) and the TAL1 polypeptide (ATGGT). TAL1 heterodimers with DNA-binding activity are readily detected in nuclear extracts of Jurkat, a leukemic cell line derived from a patient with T-cell acute lymphoblastic leukemia. Hence, TAL1 is likely to bind and regulate the transcription of a unique subset of subordinate target genes, some of which may mediate the malignant function of TAL1 during T-cell leukemogenesis.
25
Hsu, H. L., L. Huang, J. T. Tsan, W. Funk, W. E. Wright, J. S. Hu, R. E. Kingston e R. Baer. "Preferred sequences for DNA recognition by the TAL1 helix-loop-helix proteins." Molecular and Cellular Biology 14, n. 2 (febbraio 1994): 1256–65. http://dx.doi.org/10.1128/mcb.14.2.1256.
Testo completoAbstract (sommario):
Tumor-specific activation of the TAL1 gene is the most common genetic alteration seen in patients with T-cell acute lymphoblastic leukemia. The TAL1 gene products contain the basic helix-loop-helix (bHLH) domain, a protein dimerization and DNA-binding motif common to several known transcription factors. A binding-site selection procedure has now been used to evaluate the DNA recognition properties of TAL1. These studies demonstrate that TAL1 polypeptides do not have intrinsic DNA-binding activity, presumably because of their inability to form bHLH homodimers. However, TAL1 readily interacts with any of the known class A bHLH proteins (E12, E47, E2-2, and HEB) to form heterodimers that bind DNA in a sequence-specific manner. The TAL1 heterodimers preferentially recognize a subset of E-box elements (CANNTG) that can be represented by the consensus sequence AACAGATGGT. This consensus is composed of half-sites for recognition by the participating class A bHLH polypeptide (AACAG) and the TAL1 polypeptide (ATGGT). TAL1 heterodimers with DNA-binding activity are readily detected in nuclear extracts of Jurkat, a leukemic cell line derived from a patient with T-cell acute lymphoblastic leukemia. Hence, TAL1 is likely to bind and regulate the transcription of a unique subset of subordinate target genes, some of which may mediate the malignant function of TAL1 during T-cell leukemogenesis.
26
Hauser, Jannek, Juha Saarikettu e Thomas Grundström. "Calcium Regulation of Myogenesis by Differential Calmodulin Inhibition of Basic Helix-Loop-Helix Transcription Factors". Molecular Biology of the Cell 19, n. 6 (giugno 2008): 2509–19. http://dx.doi.org/10.1091/mbc.e07-09-0886.
Testo completoAbstract (sommario):
The members of the MyoD family of basic helix-loop-helix (bHLH) transcription factors are critical regulators of skeletal muscle differentiation that function as heterodimers with ubiquitously expressed E-protein bHLH transcription factors. These heterodimers must compete successfully with homodimers of E12 and other E-proteins to enable myogenesis. Here, we show that E12 mutants resistant to Ca2+-loaded calmodulin (CaM) inhibit MyoD-initiated myogenic conversion of transfected fibroblasts. Ca2+ channel blockers reduce, and Ca2+ stimulation increases, transcription by coexpressed MyoD and wild-type E12 but not CaM-resistant mutant E12. Furthermore, CaM-resistant E12 gives lower MyoD binding and higher E12 binding to a MyoD-responsive promoter in vivo and cannot rescue myogenic differentiation that has been inhibited by siRNA against E12 and E47. Our data support the concept that Ca2+-loaded CaM enables myogenesis by inhibiting DNA binding of E-protein homodimers, thereby promoting occupancy of myogenic bHLH protein/E-protein heterodimers on promoters of myogenic target genes.
27
Sánchez-Pérez, R., S. Pavan, R. Mazzeo, C. Moldovan, R. Aiese Cigliano, J. Del Cueto, F. Ricciardi et al. "Mutation of a bHLH transcription factor allowed almond domestication". Science 364, n. 6445 (13 giugno 2019): 1095–98. http://dx.doi.org/10.1126/science.aav8197.
Testo completoAbstract (sommario):
Wild almond species accumulate the bitter and toxic cyanogenic diglucoside amygdalin. Almond domestication was enabled by the selection of genotypes harboring sweet kernels. We report the completion of the almond reference genome. Map-based cloning using an F1 population segregating for kernel taste led to the identification of a 46-kilobase gene cluster encoding five basic helix-loop-helix transcription factors, bHLH1 to bHLH5. Functional characterization demonstrated that bHLH2 controls transcription of the P450 monooxygenase–encoding genes PdCYP79D16 and PdCYP71AN24, which are involved in the amygdalin biosynthetic pathway. A nonsynonymous point mutation (Leu to Phe) in the dimerization domain of bHLH2 prevents transcription of the two cytochrome P450 genes, resulting in the sweet kernel trait.
28
Martínez, C., J. Modolell e J. Garrell. "Regulation of the proneural gene achaete by helix-loop-helix proteins". Molecular and Cellular Biology 13, n. 6 (giugno 1993): 3514–21. http://dx.doi.org/10.1128/mcb.13.6.3514-3521.1993.
Testo completoAbstract (sommario):
The Achaete (Ac) protein, a transcriptional regulator of the basic-helix-loop-helix (bHLH) type, confers upon ectodermal cells the ability to become neural precursors. Its temporally and spatially regulated expression, together with that of the related Scute (Sc) protein, helps define the pattern of Drosophila melanogaster sensory organs. We have examined the transcriptional control of the ac gene and shown, using in vivo assays, that several E-boxes, putative interacting sites for bHLH proteins, present in the ac promoter are most important for ac regulation. They most likely mediate ac self-stimulation and sc trans-activation. We also demonstrate that ac transcription is negatively regulated in vivo by the gene extramacrochaetae (emc) in a manner dependent on Ac and Sc products. emc encodes an HLH protein that lacks the basic region and presumably antagonizes Ac and Sc function by sequestering these proteins in complexes unable to interact with DNA. Our results strongly support the model of negative regulation of emc on ac and sc transcription through titration of their products. As currently thought, this seems accomplished by heterodimerization via the HLH domain, because an amino acid substitution in this region abolishes the emc antagonistic effect both in vitro and in vivo.
29
Martínez, C., J. Modolell e J. Garrell. "Regulation of the proneural gene achaete by helix-loop-helix proteins." Molecular and Cellular Biology 13, n. 6 (giugno 1993): 3514–21. http://dx.doi.org/10.1128/mcb.13.6.3514.
Testo completoAbstract (sommario):
The Achaete (Ac) protein, a transcriptional regulator of the basic-helix-loop-helix (bHLH) type, confers upon ectodermal cells the ability to become neural precursors. Its temporally and spatially regulated expression, together with that of the related Scute (Sc) protein, helps define the pattern of Drosophila melanogaster sensory organs. We have examined the transcriptional control of the ac gene and shown, using in vivo assays, that several E-boxes, putative interacting sites for bHLH proteins, present in the ac promoter are most important for ac regulation. They most likely mediate ac self-stimulation and sc trans-activation. We also demonstrate that ac transcription is negatively regulated in vivo by the gene extramacrochaetae (emc) in a manner dependent on Ac and Sc products. emc encodes an HLH protein that lacks the basic region and presumably antagonizes Ac and Sc function by sequestering these proteins in complexes unable to interact with DNA. Our results strongly support the model of negative regulation of emc on ac and sc transcription through titration of their products. As currently thought, this seems accomplished by heterodimerization via the HLH domain, because an amino acid substitution in this region abolishes the emc antagonistic effect both in vitro and in vivo.
30
Kondo, T., e M. Raff. "Basic helix-loop-helix proteins and the timing of oligodendrocyte differentiation". Development 127, n. 14 (15 luglio 2000): 2989–98. http://dx.doi.org/10.1242/dev.127.14.2989.
Testo completoAbstract (sommario):
An intracellular timer in oligodendrocyte precursor cells is thought to help control the timing of their differentiation. We show here that the expression of the Hes5 and Mash1 genes, which encode neural-specific bHLH proteins, decrease and increase, respectively, in these cells with a time course expected if the proteins are part of the timer. We show that enforced expression of Hes5 in purified precursor cells strongly inhibits the normal increase in the thyroid hormone receptor protein TR(β)1, which is thought to be part of the timing mechanism; it also strongly inhibits the differentiation induced by either mitogen withdrawal or thyroid hormone treatment. Enforced expression of Mash1, by contrast, somewhat accelerates the increase in TR(beta)1 protein. These findings suggest that Hes5 and Mash1 may be part of the cell-intrinsic timer in the precursor cells.
31
Ke, Qinglin, Wenjing Tao, Tingting Li, Wenqiu Pan, Xiaoyun Chen, Xiaoyu Wu, Xiaojun Nie e Licao Cui. "Genome-wide Identification, Evolution and Expression Analysis of Basic Helix-loop-helix (bHLH) Gene Family in Barley (Hordeum vulgare L.)". Current Genomics 21, n. 8 (21 dicembre 2020): 624–44. http://dx.doi.org/10.2174/1389202921999201102165537.
Testo completoAbstract (sommario):
Background: The basic helix-loop-helix (bHLH) transcription factor is one of the most important gene families in plants, playing a key role in diverse metabolic, physiological, and developmental processes. Although it has been well characterized in many plants, the significance of the bHLH family in barley is not well understood at present. Methods: Through a genome-wide search against the updated barley reference genome, the genomic organization, evolution and expression of the bHLH family in barley were systematically analyzed. Results: We identified 141 bHLHs in the barley genome (HvbHLHs) and further classified them into 24 subfamilies based on phylogenetic analysis. It was found that HvbHLHs in the same subfamily shared a similar conserved motif composition and exon-intron structures. Chromosome distribution and gene duplication analysis revealed that segmental duplication mainly contributed to the expansion of HvbHLHs and the duplicated genes were subjected to strong purifying selection. Furthermore, expression analysis revealed that HvbHLHs were widely expressed in different tissues and also involved in response to diverse abiotic stresses. The co-expression network was further analyzed to underpin the regulatory function of HvbHLHs. Finally, 25 genes were selected for qRT-PCR validation, the expression profiles of HvbHLHs showed diverse patterns, demonstrating their potential roles in relation to stress tolerance regulation. Conclusion: This study reported the genome organization, evolutionary characteristics and expression profile of the bHLH family in barley, which not only provide the targets for further functional analysis, but also facilitate better understanding of the regulatory network bHLH genes involved in stress tolerance in barley.
32
Yang, Min, Chenping Zhou, Hu Yang, Ruibin Kuang, Bingxiong Huang e Yuerong Wei. "Genome-wide analysis of basic helix-loop-helix transcription factors in papaya (Carica papaya L.)". PeerJ 8 (3 luglio 2020): e9319. http://dx.doi.org/10.7717/peerj.9319.
Testo completoAbstract (sommario):
The basic helix-loop-helix (bHLH) transcription factors (TFs) have been identified and functionally characterized in many plants. However, no comprehensive analysis of the bHLH family in papaya (Carica papaya L.) has been reported previously. Here, a total of 73 CpbHLHs were identified in papaya, and these genes were classified into 18 subfamilies based on phylogenetic analysis. Almost all of the CpbHLHs in the same subfamily shared similar gene structures and protein motifs according to analysis of exon/intron organizations and motif compositions. The number of exons in CpbHLHs varied from one to 10 with an average of five. The amino acid sequences of the bHLH domains were quite conservative, especially Leu-27 and Leu-63. Promoter cis-element analysis revealed that most of the CpbHLHs contained cis-elements that can respond to various biotic/abiotic stress-related events. Gene ontology (GO) analysis revealed that CpbHLHs mainly functions in protein dimerization activity and DNA-binding, and most CpbHLHs were predicted to localize in the nucleus. Abiotic stress treatment and quantitative real-time PCR (qRT-PCR) revealed some important candidate CpbHLHs that might be responsible for abiotic stress responses in papaya. These findings would lay a foundation for further investigate of the molecular functions of CpbHLHs.
33
Rao, S. S., C. Chu e D. S. Kohtz. "Ectopic expression of cyclin D1 prevents activation of gene transcription by myogenic basic helix-loop-helix regulators". Molecular and Cellular Biology 14, n. 8 (agosto 1994): 5259–67. http://dx.doi.org/10.1128/mcb.14.8.5259-5267.1994.
Testo completoAbstract (sommario):
Activation of muscle gene transcription in differentiating skeletal myoblasts requires their withdrawal from the cell cycle. The effects of ectopic cyclin expression on activation of muscle gene transcription by myogenic basic helix-loop-helix (bHLH) regulators were investigated. Ectopic expression of cyclin D1, but not cyclins A, B1, B2, C, D3, and E, inhibited transcriptional activation of muscle gene reporter constructs by myogenic bHLH regulators in a dose-dependent manner. Ectopic expression of cyclin D1 inhibited the activity of a myogenic bHLH regulator mutant lacking the basic region protein kinase C site, indicating that phosphorylation of this site is not relevant to the mechanism of inhibition. Analysis of cyclin D1 mutants revealed that the C-terminal acidic region was required for inhibition of myogenic bHLH regulator activity, whereas an intact N-terminal pRb binding motif was not essential. Together, these results implicate expression of cyclin D1 as a central determinant of a putatively novel mechanism that links positive control of cell cycle progression to negative regulation of genes expressed in differentiated myocytes.
34
Rao, S. S., C. Chu e D. S. Kohtz. "Ectopic expression of cyclin D1 prevents activation of gene transcription by myogenic basic helix-loop-helix regulators." Molecular and Cellular Biology 14, n. 8 (agosto 1994): 5259–67. http://dx.doi.org/10.1128/mcb.14.8.5259.
Testo completoAbstract (sommario):
Activation of muscle gene transcription in differentiating skeletal myoblasts requires their withdrawal from the cell cycle. The effects of ectopic cyclin expression on activation of muscle gene transcription by myogenic basic helix-loop-helix (bHLH) regulators were investigated. Ectopic expression of cyclin D1, but not cyclins A, B1, B2, C, D3, and E, inhibited transcriptional activation of muscle gene reporter constructs by myogenic bHLH regulators in a dose-dependent manner. Ectopic expression of cyclin D1 inhibited the activity of a myogenic bHLH regulator mutant lacking the basic region protein kinase C site, indicating that phosphorylation of this site is not relevant to the mechanism of inhibition. Analysis of cyclin D1 mutants revealed that the C-terminal acidic region was required for inhibition of myogenic bHLH regulator activity, whereas an intact N-terminal pRb binding motif was not essential. Together, these results implicate expression of cyclin D1 as a central determinant of a putatively novel mechanism that links positive control of cell cycle progression to negative regulation of genes expressed in differentiated myocytes.
35
Haberland, Michael, Michael A. Arnold, John McAnally, Dillon Phan, Yuri Kim e Eric N. Olson. "Regulation of HDAC9 Gene Expression by MEF2 Establishes a Negative-Feedback Loop in the Transcriptional Circuitry of Muscle Differentiation". Molecular and Cellular Biology 27, n. 2 (13 novembre 2006): 518–25. http://dx.doi.org/10.1128/mcb.01415-06.
Testo completoAbstract (sommario):
ABSTRACT Skeletal muscle development is controlled by the myocyte enhancer factor (MEF2) and myogenic basic helix-loop-helix (bHLH) families of transcription factors, which associate and synergistically activate muscle gene expression. Muscle differentiation is further reinforced by positive-feedback loops in which myogenic bHLH proteins activate their own expression and the expression of MEF2, while MEF2 stimulates expression of myogenic bHLH genes and the Mef2c gene. Here we describe a myogenic negative-feedback loop that consists of MEF2 proteins and the transcriptional repressor histone deacetylase 9 (HDAC9). We show that the HDAC9 gene is a direct transcriptional target of MEF2 in vitro and in vivo. HDAC9 can associate with MEF2 proteins and suppress their transcriptional activity. The transcriptional repressor HDAC9 thus forms a negative-feedback loop in the transcriptional circuitry of muscle differentiation.
36
Massari, Mark Eben, Richard R. Rivera, Joseph R. Voland, Melanie W. Quong, Timo M. Breit, Jacques J. M. van Dongen, Oncko de Smit e Cornelis Murre. "Characterization of ABF-1, a Novel Basic Helix-Loop-Helix Transcription Factor Expressed in Activated B Lymphocytes". Molecular and Cellular Biology 18, n. 6 (1 giugno 1998): 3130–39. http://dx.doi.org/10.1128/mcb.18.6.3130.
Testo completoAbstract (sommario):
ABSTRACT Proteins of the basic helix-loop-helix (bHLH) family are required for a number of different developmental pathways, including neurogenesis, lymphopoiesis, myogenesis, and sex determination. Using a yeast two-hybrid screen, we have identified a new bHLH transcription factor, ABF-1, from a human B-cell cDNA library. Within the bHLH region, ABF-1 shows a remarkable conservation with other HLH proteins, including tal-1, NeuroD, and paraxis. Its expression pattern is restricted to a subset of lymphoid tissues, Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines, and activated human B cells. ABF-1 is capable of binding an E-box element either as a homodimer or as a heterodimer with E2A. Furthermore, a heterodimeric complex containing ABF-1 and E2A can be detected in EBV-immortalized lymphoblastoid cell lines. ABF-1 contains a transcriptional repression domain and is capable of inhibiting the transactivation capability of E47 in mammalian cells. ABF-1 represents the first example of a B-cell-restricted bHLH protein, and its expression pattern suggests that ABF-1 may play a role in regulating antigen-dependent B-cell differentiation.
37
Wang, Zhi, e William R. Atchley. "Spectral Analysis of Sequence Variability in Basic-Helix-loop-helix (bHLH) Protein Domains". Evolutionary Bioinformatics 2 (gennaio 2006): 117693430600200. http://dx.doi.org/10.1177/117693430600200001.
Testo completo
38
Sun, X. H., N. G. Copeland, N. A. Jenkins e D. Baltimore. "Id proteins Id1 and Id2 selectively inhibit DNA binding by one class of helix-loop-helix proteins". Molecular and Cellular Biology 11, n. 11 (novembre 1991): 5603–11. http://dx.doi.org/10.1128/mcb.11.11.5603-5611.1991.
Testo completoAbstract (sommario):
The DNA binding activities of some basic region and putative helix-loop-helix (bHLH)-containing transcriptional factors can be inhibited by the Id protein. Because Id contains the HLH motif for dimerization but not the basic amino acid region for DNA binding, heterodimers of Id with bHLH transcriptional factors may not bind to DNA. We have isolated and characterized the gene and cDNA clones for a new Id protein, designated Id2. The Id2 protein contains a helix-loop-helix motif similar to that of the previously described Id protein (referred to here as Id1), but the two proteins are different elsewhere. Id1 and Id2 are encoded by two unlinked genes, as shown by chromosome mapping. The two Id proteins have similar inhibitory activities. They selectively bind to and inhibit the function of one set of bHLH proteins, typified by E2A.E47 and E2B.m3, but not that of the other set, including TFE3, USF, and AP4. The Id proteins also homodimerize poorly. Expression of both Id genes is down-regulated during differentiation in a variety of cell types.
39
Sun, X. H., N. G. Copeland, N. A. Jenkins e D. Baltimore. "Id proteins Id1 and Id2 selectively inhibit DNA binding by one class of helix-loop-helix proteins." Molecular and Cellular Biology 11, n. 11 (novembre 1991): 5603–11. http://dx.doi.org/10.1128/mcb.11.11.5603.
Testo completoAbstract (sommario):
The DNA binding activities of some basic region and putative helix-loop-helix (bHLH)-containing transcriptional factors can be inhibited by the Id protein. Because Id contains the HLH motif for dimerization but not the basic amino acid region for DNA binding, heterodimers of Id with bHLH transcriptional factors may not bind to DNA. We have isolated and characterized the gene and cDNA clones for a new Id protein, designated Id2. The Id2 protein contains a helix-loop-helix motif similar to that of the previously described Id protein (referred to here as Id1), but the two proteins are different elsewhere. Id1 and Id2 are encoded by two unlinked genes, as shown by chromosome mapping. The two Id proteins have similar inhibitory activities. They selectively bind to and inhibit the function of one set of bHLH proteins, typified by E2A.E47 and E2B.m3, but not that of the other set, including TFE3, USF, and AP4. The Id proteins also homodimerize poorly. Expression of both Id genes is down-regulated during differentiation in a variety of cell types.
40
Tian, Shiyu, Lujun Li, Min Wei e Fengjuan Yang. "Genome-wide analysis of basic helix–loop–helix superfamily members related to anthocyanin biosynthesis in eggplant (Solanum melongena L.)". PeerJ 7 (9 ottobre 2019): e7768. http://dx.doi.org/10.7717/peerj.7768.
Testo completoAbstract (sommario):
The basic helix–loop–helix (bHLH) superfamily is considered the second largest transcription factor (TF) family. It plays regulatory roles in the developmental processes of plants and in their defense responses. In recent years, many bHLH superfamily genes have been identified and characterized in herbaceous and woody plants. However, the comprehensive genomic and functional analyses of these genes in eggplant (Solanum melongena L.) have not been reported. In this study, 121 bHLH TFs were identified in the recently released eggplant genome. The phylogeny, gene structure and conserved motifs of the SmbHLH gene were comprehensively studied. Subsequently, the phylogenetic relationship between the bHLH of eggplant and the bHLH of other species was analyzed, and the proteins were classified into 17 subfamilies. Among these protein sequences, 16 subgroups were clustered into the functional clades of Arabidopsis. Two candidate genes (SmbHLH1, SmbHLH117) that may be involved in anthocyanin biosynthesis were screened. The tissue specificity or differential expression of the bHLH genes in different tissues and under various light and temperature conditions suggested the differential regulation of tissue development and metabolism. This study not only provides a solid foundation for the functional dissection of the eggplant bHLH gene family but may also be useful for the future synthesis of anthocyanins in eggplant.
41
Chiaramello, A., K. Neuman, K. Palm, M. Metsis e T. Neuman. "Helix-loop-helix transcription factors mediate activation and repression of the p75LNGFR gene." Molecular and Cellular Biology 15, n. 11 (novembre 1995): 6036–44. http://dx.doi.org/10.1128/mcb.15.11.6036.
Testo completoAbstract (sommario):
Sequence analysis of rat and human low-affinity nerve growth factor receptor p75LNGFR gene promoter regions revealed a single E-box cis-acting element, located upstream of the major transcription start sites. Deletion analysis of the E-box sequence demonstrated that it significantly contributes to p75LNGFR promoter activity. This E box has a dual function; it mediates either activation or repression of the p75LNGFR promoter activity, depending on the interacting transcription factors. We showed that the two isoforms of the class A basic helix-loop-helix (bHLH) transcription factor ME1 (ME1a and ME1b), the murine homolog of the human HEB transcription factor, specifically repress p75LNGFR promoter activity. This repression can be released by coexpression of the HLH Id2 transcriptional regulator. In vitro analyses demonstrated that ME1a forms a stable complex with the p75LNGFR E box and likely competes with activating E-box-binding proteins. By using ME1a-overexpressing PC12 cells, we showed that the endogenous p75LNGFR gene is a target of ME1a repression. Together, these data demonstrate that the p75LNGFR E box and the interacting bHLH transcription factors are involved in the regulation of p75LNGFR gene expression. These results also show that class A bHLH transcription factors can repress and Id-like negative regulators can stimulate gene expression.
42
Tontonoz, P., J. B. Kim, R. A. Graves e B. M. Spiegelman. "ADD1: a novel helix-loop-helix transcription factor associated with adipocyte determination and differentiation". Molecular and Cellular Biology 13, n. 8 (agosto 1993): 4753–59. http://dx.doi.org/10.1128/mcb.13.8.4753-4759.1993.
Testo completoAbstract (sommario):
DNA-binding proteins containing the basic helix-loop-helix (bHLH) domain have been implicated in lineage determination and the regulation of specific gene expression in a number of cell types. By oligonucleotide screening of an adipocyte cDNA expression library, we have identified a novel member of the bHLH-leucine zipper transcription factor family designated ADD1. ADD1 mRNA is expressed predominantly in brown adipose tissue in vivo and is regulated during both determination and differentiation of cultured adipocyte cell lines. ADD1 can function as a sequence-specific transcriptional activator in that it stimulates expression of a chloramphenicol acetyltransferase vector containing multiple ADD1 binding sequences but is unable to activate the myosin light-chain enhancer, which contains multiple binding sites for another bHLH factor, MyoD. ADD1 can also activate transcription through a binding site present in the 5'-flanking region of the fatty acid synthetase gene which is expressed in a differentiation-dependent manner in adipose cells. These data suggest that ADD1 plays a role in the regulation of determination- and differentiation-specific gene expression in adipocytes.
43
Tontonoz, P., J. B. Kim, R. A. Graves e B. M. Spiegelman. "ADD1: a novel helix-loop-helix transcription factor associated with adipocyte determination and differentiation." Molecular and Cellular Biology 13, n. 8 (agosto 1993): 4753–59. http://dx.doi.org/10.1128/mcb.13.8.4753.
Testo completoAbstract (sommario):
DNA-binding proteins containing the basic helix-loop-helix (bHLH) domain have been implicated in lineage determination and the regulation of specific gene expression in a number of cell types. By oligonucleotide screening of an adipocyte cDNA expression library, we have identified a novel member of the bHLH-leucine zipper transcription factor family designated ADD1. ADD1 mRNA is expressed predominantly in brown adipose tissue in vivo and is regulated during both determination and differentiation of cultured adipocyte cell lines. ADD1 can function as a sequence-specific transcriptional activator in that it stimulates expression of a chloramphenicol acetyltransferase vector containing multiple ADD1 binding sequences but is unable to activate the myosin light-chain enhancer, which contains multiple binding sites for another bHLH factor, MyoD. ADD1 can also activate transcription through a binding site present in the 5'-flanking region of the fatty acid synthetase gene which is expressed in a differentiation-dependent manner in adipose cells. These data suggest that ADD1 plays a role in the regulation of determination- and differentiation-specific gene expression in adipocytes.
44
Taylor, D. A., V. B. Kraus, J. J. Schwarz, E. N. Olson e W. E. Kraus. "E1A-mediated inhibition of myogenesis correlates with a direct physical interaction of E1A12S and basic helix-loop-helix proteins". Molecular and Cellular Biology 13, n. 8 (agosto 1993): 4714–27. http://dx.doi.org/10.1128/mcb.13.8.4714-4727.1993.
Testo completoAbstract (sommario):
The observation that adenovirus E1A gene products can inhibit differentiation of skeletal myocytes suggested that E1A may interfere with the activity of myogenic basic helix-loop-helix (bHLH) transcription factors. We have examined the ability of E1A to mediate repression of the muscle-specific creatine kinase (MCK) gene. Both the E1A12S and E1A13S products repressed MCK transcription in a concentration-dependent fashion. In contrast, amino-terminal deletion mutants (d2-36 and d15-35) of E1A12S were defective for repression. E1A12S also repressed expression of a promoter containing a multimer of the MCK high-affinity E box (the consensus site for myogenic bHLH protein binding) that was dependent, in C3H10T1/2 cells, on coexpression of a myogenin bHLH-VP16 fusion protein. A series of coprecipitation experiments with glutathione S-transferase fusion and in vitro-translated proteins demonstrated that E1A12S, but not amino-terminal E1A deletion mutants, could bind to full-length myogenin and E12 and to deletion mutants of myogenin and E12 that spare the bHLH domains. Thus, the bHLH domains of myogenin and E12, and the high-affinity E box, are targets for E1A-mediated repression of the MCK enhancer, and domains of E1A required for repression of muscle-specific gene transcription also mediate binding to bHLH proteins. We conclude that E1A mediates repression of muscle-specific gene transcription through its amino-terminal domain and propose that this may involve a direct physical interaction between E1A and the bHLH region of myogenic determination proteins.
45
Taylor, D. A., V. B. Kraus, J. J. Schwarz, E. N. Olson e W. E. Kraus. "E1A-mediated inhibition of myogenesis correlates with a direct physical interaction of E1A12S and basic helix-loop-helix proteins." Molecular and Cellular Biology 13, n. 8 (agosto 1993): 4714–27. http://dx.doi.org/10.1128/mcb.13.8.4714.
Testo completoAbstract (sommario):
The observation that adenovirus E1A gene products can inhibit differentiation of skeletal myocytes suggested that E1A may interfere with the activity of myogenic basic helix-loop-helix (bHLH) transcription factors. We have examined the ability of E1A to mediate repression of the muscle-specific creatine kinase (MCK) gene. Both the E1A12S and E1A13S products repressed MCK transcription in a concentration-dependent fashion. In contrast, amino-terminal deletion mutants (d2-36 and d15-35) of E1A12S were defective for repression. E1A12S also repressed expression of a promoter containing a multimer of the MCK high-affinity E box (the consensus site for myogenic bHLH protein binding) that was dependent, in C3H10T1/2 cells, on coexpression of a myogenin bHLH-VP16 fusion protein. A series of coprecipitation experiments with glutathione S-transferase fusion and in vitro-translated proteins demonstrated that E1A12S, but not amino-terminal E1A deletion mutants, could bind to full-length myogenin and E12 and to deletion mutants of myogenin and E12 that spare the bHLH domains. Thus, the bHLH domains of myogenin and E12, and the high-affinity E box, are targets for E1A-mediated repression of the MCK enhancer, and domains of E1A required for repression of muscle-specific gene transcription also mediate binding to bHLH proteins. We conclude that E1A mediates repression of muscle-specific gene transcription through its amino-terminal domain and propose that this may involve a direct physical interaction between E1A and the bHLH region of myogenic determination proteins.
46
Norton, J. D. "ID helix-loop-helix proteins in cell growth, differentiation and tumorigenesis". Journal of Cell Science 113, n. 22 (15 novembre 2000): 3897–905. http://dx.doi.org/10.1242/jcs.113.22.3897.
Testo completoAbstract (sommario):
The ubiquitously expressed family of ID helix-loop-helix (HLH) proteins function as dominant negative regulators of basic HLH (bHLH) transcriptional regulators that drive cell lineage commitment and differentiation in metazoa. Recent data from cell line and in vivo studies have implicated the functions of ID proteins in other cellular processes besides negative regulation of cell differentiation. ID proteins play key roles in the regulation of lineage commitment, cell fate decisions and in the timing of differentiation during neurogenesis, lymphopoiesis and neovascularisation (angiogenesis). They are essential for embryogenesis and for cell cycle progression, and they function as positive regulators of cell proliferation. ID proteins also possess pro-apoptotic properties in a variety of cell types and function as cooperating or dominant oncoproteins in immortalisation of rodent and human cells and in tumour induction in Id-transgenic mice. In several human tumour types, the expression of ID proteins is deregulated, and loss- and gain-of-function studies implicate ID functions in the regulation of tumour growth, vascularisation, invasiveness and metastasis. More recent biochemical studies have also revealed an emerging ‘molecular promiscuity’ of mammalian ID proteins: they directly interact with and modulate the activities of several other families of transcriptional regulator, besides bHLH proteins.
47
Liu, Wuyi, e Deyu Chen. "Phylogeny, Functional Annotation, and Protein Interaction Network Analyses of theXenopus tropicalisBasic Helix-Loop-Helix Transcription Factors". BioMed Research International 2013 (2013): 1–15. http://dx.doi.org/10.1155/2013/145037.
Testo completoAbstract (sommario):
The previous survey identified 70 basic helix-loop-helix (bHLH) proteins, but it was proved to be incomplete, and the functional information and regulatory networks of frog bHLH transcription factors were not fully known. Therefore, we conducted an updated genome-wide survey in theXenopus tropicalisgenome project databases and identified 105 bHLH sequences. Among the retrieved 105 sequences, phylogenetic analyses revealed that 103 bHLH proteins belonged to 43 families or subfamilies with 46, 26, 11, 3, 15, and 4 members in the corresponding supergroups. Next, gene ontology (GO) enrichment analyses showed 65 significant GO annotations of biological processes and molecular functions and KEGG pathways counted in frequency. To explore the functional pathways, regulatory gene networks, and/or related gene groups coding forXenopus tropicalisbHLH proteins, the identified bHLH genes were put into the databases KOBAS and STRING to get the signaling information of pathways and protein interaction networks according to available public databases and known protein interactions. From the genome annotation and pathway analysis using KOBAS, we identified 16 pathways in theXenopus tropicalisgenome. From the STRING interaction analysis, 68 hub proteins were identified, and many hub proteins created a tight network or a functional module within the protein families.
48
Koch, Marilin, Stefan Czemmel, Felix Lennartz, Sarah Beyeler, Justyna Przystal, Parameswari Govindarajan, Denis Canjuga et al. "CSIG-15. INHIBITION OF THE bHLH TRANSCRIPTIONAL NETWORKS BY A MUTATED E47 PROTEIN LEADS TO A STRONG ANTI-GLIOMA ACTIVITY IN VITRO AND IN VIVO". Neuro-Oncology 21, Supplement_6 (novembre 2019): vi47. http://dx.doi.org/10.1093/neuonc/noz175.185.
Testo completoAbstract (sommario):
Abstract OBJECTIVE The transcription factor E47 heterodimerizes with helix-loop-helix (HLH) and basic helix-loop-helix transcription (bHLH) factors like ID-1 and Olig2 that are overexpressed in glioblastoma. A dominant-negative variant of the E47 (dnE47) lacking the nuclear translocation signal, leads to cytoplasmatic sequestration of HLH and bHLH transcription factors. Here, we investigated combinations of dnE47-mediated inhibition of the bHLH transcriptional network with temozolomide and irradiation and explored the underlying molecular mechanisms. METHODS Long-term and stem cell glioma lines were transduced with a Doxycycline-inducible dnE47 lentivirus. Functional characterizations included immunocytochemistry, immunoblots, cytotoxicity and clonogenicity assays in vitro and latency until the onset of symptoms in vivo. CAGE and RNASeq were conducted for analyzing the dnE47-induced molecular profile. RESULTS The induction of dnE47 led to cytoplasmatic sequestration of HLH/bHLH transcription, reduced proliferation, increased cytotoxicity and reduced clonogenic survival in vitro and a prolonged latency until the onset of neurological symptoms in vivo. CAGE and RNASeq data revealed alterations in several cancer-relevant pathways. CONCLUSIONS A dnE47-mediated inhibition of the bHLH transcription network induced actionable molecular alterations in glioma cells that could be exploited for the design of novel therapies.
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Schlaeger, Thorsten M., Anna Schuh, Simon Flitter, Andreas Fisher, Hanna Mikkola, Stuart H. Orkin, Paresh Vyas e Catherine Porcher. "Decoding Hematopoietic Specificity in the Helix-Loop-Helix Domain of the Transcription Factor SCL/Tal-1". Molecular and Cellular Biology 24, n. 17 (1 settembre 2004): 7491–502. http://dx.doi.org/10.1128/mcb.24.17.7491-7502.2004.
Testo completoAbstract (sommario):
ABSTRACT The helix-loop-helix (HLH) domain is employed by many transcription factors that control cell fate choice in multiple developmental settings. Previously, we demonstrated that the HLH domain of the class II basic HLH (bHLH) protein SCL/Tal-1 is critical for hematopoietic specification. We have now identified residues in this domain that are essential for restoring hematopoietic development to SCL−/− embryonic stem cells and sufficient to convert a muscle-specific HLH domain to one able to rescue hematopoiesis. Most of these critical residues are distributed in the loop of SCL, with one in helix 2. This is in contrast to the case for MyoD, the prototype of class II bHLH proteins, where the loop seems to serve mainly as a linker between the two helices. Among the identified residues, some promote heterodimerization with the bHLH partners of SCL (E12/E47), while others, unimportant for this property, are still crucial for the biological function of SCL. Importantly, the residue in helix 2 specifically promotes interaction with a known partner of SCL, the LIM-only protein LMO2, a finding that strengthens genetic evidence that these proteins interact. Our data highlight the functional complexity of bHLH proteins, provide mechanistic insight into SCL function, and strongly support the existence of an active SCL/LMO2-containing multiprotein complex in early hematopoietic cells.
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Liu, Xiao-Ting, Yong Wang, Xu-Hua Wang, Xia-Fang Tao, Qin Yao e Ke-Ping Chen. "A genome-wide identification and classification of basic helix-loop-helix genes in the jewel wasp, Nasonia vitripennis (Hymenoptera: Pteromalidae)". Genome 57, n. 10 (ottobre 2014): 525–36. http://dx.doi.org/10.1139/gen-2014-0171.
Testo completoAbstract (sommario):
Basic helix-loop-helix (bHLH) proteins are highly conserved DNA-binding transcription factors of a large superfamily. Animal bHLH proteins play important regulatory roles in various developmental processes such as neurogenesis, myogenesis, heart development, and hematopoiesis. The jewel wasp (Nasonia vitripennis) is a good model organism of hymenoptera insects for studies of developmental and evolutionary genetics. In this study, we identified 48 bHLH genes in the genome of N. vitripennis. According to phylogenetic analysis, based on N. vitripennis bHLH (NvbHLH) motif sequences and structural domain distribution in their full-length protein sequences, the identified NvbHLH genes were classified into 36 bHLH families with 19, 12, 9, 1, 6, and 1 member(s) in groups A, B, C, D, E, and F, respectively. Our classification to the identified NvbHLH family members confirms GenBank annotations for 21 of the 48 NvbHLH proteins and provides useful information for further characterization and annotation of the remaining 27 NvbHLH proteins. Compared to other insect species, N. vitripennis has the lowest number of bHLH family members. No NvbHLH members have been found in the families Net, MyoRa, and PTFa, while all other insect species have at least one member in each of the families. These data constitute a solid basis for further investigations into the functions of bHLH proteins in developmental regulation of N. vitripennis.