Academic literature on the topic 'C17-c25'

ABSTRACT The essential C17 subunit of yeast RNA polymerase (Pol) III interacts with Brf1, a component of TFIIIB, suggesting a role for C17 in the initiation step of transcription. The protein sequence of C17 (encoded by RPC17) is conserved from yeasts to humans. However, mammalian homologues of C17 (named CGRP-RCP) are known to be involved in a signal transduction pathway related to G protein-coupled receptors, not in transcription. In the present work, we first establish that human CGRP-RCP is the genuine orthologue of C17. CGRP-RCP was found to functionally replace C17 in Δrpc17 yeast cells; the purified mutant Pol III contained CGRP-RCP and had a decreased specific activity but initiated faithfully. Furthermore, CGRP-RCP was identified by mass spectrometry in a highly purified human Pol III preparation. These results suggest that CGRP-RCP has a dual function in mammals. Next, we demonstrate by genetic and biochemical approaches that C17 forms with C25 (encoded by RPC25) a heterodimer akin to Rpb4/Rpb7 in Pol II. C17 and C25 were found to interact genetically in suppression screens and physically in coimmunopurification and two-hybrid experiments. Sequence analysis and molecular modeling indicated that the C17/C25 heterodimer likely adopts a structure similar to that of the archaeal RpoE/RpoF counterpart of the Rpb4/Rpb7 complex. These RNA polymerase subunits appear to have evolved to meet the distinct requirements of the multiple forms of RNA polymerases.

Abstract Fusarium culmorum F1 was found to produce and secrete into the culture medium several of 5-n-alkylresorcinols. The amount of resorcinolic lipids was 5.3 μg/g and 0.9 μg/l in mycelium and in post-culture liquid, respectively. First of all F. culmorum F1 produces saturated homologues with C15 to C25 side chains. The extract from the medium contained only homologues with shorter carbon chains (C13 to C17).

Acetone extracts from the seeds of Pisum sativum L. sensu lato (Leguminoseae) separated by thin layer chromatography revealed the occurrence of hands with chromatographic mobility and color reaction with Fast Blue B characteristic for 1,3-dihydroxy-5-alkyIbenzenes. These polyketide metabolites have been isolated and identified by Spectroscopic means. The occurrence of homologous series of saturated (approximately 70%) and enoic (mono and diunsaturated) homologs with chain length of C15 to C25 has been revealed with C17 as the main homolog

Chemical investigation of MeOH extract of a South China Sea sponge Cacospongia sp. yielded 15 terpenoids belonging to three different skeleton-types, including the unusual C17 γ-lactone norditerpenoids (1–3), the rare C21 pyridine meroterpenoid (7), and the notable C25 manoalide-type sesterterpenoids (4–6, 8–10). Compounds 1–5 were initially obtained as enantiomers, and were further separated to be optically pure compounds (1a, 1b, 2a, 2b, 3a-r, 3b-r, 4a, 4b, 5a and 5b) by chiral HPLC, with a LiAlH4 reduction aid for 3. Compounds 3a/3b (a pair of inseparable enantiomers), 4a, 5a, 6, and 7 were identified as new compounds, while 1a/1b and 2a/2b were obtained from a natural source and were determined for their absolute configurations for the first time. This is also the first time to encounter enantiomers of the well-known manoalide-type sesterterpenoids from nature. The structures with absolute configurations of the new compounds were unambiguously determined by comprehensive methods including HR-ESI-MS and NMR data analysis, optical rotation comparison, experimental and calculated electronic circular dichroism (ECD), and Mo2(OAc)4 induced circular dichroism (ICD) methods. The cytotoxicity of the isolates against selected human tumor cell lines was evaluated, however, the tested compounds showed no activity against selected cell lines.

Dihydroergocristine methanesulfonate monohydrate crystallizes in orthorhorhombic space group P21212 (No. 18) with Z = 4, a = 12.736(2) Å, b = 39.089(5) Å, c = 7.130(1) Å, V = 3549.6(9) Å3. The indole moiety is nearly planar, both the ergoline ring C and the tripeptide ring F addopt an envelope E6 conformation. The ergoline ring D and the tripeptide ring E have a chair 1C4 conformation. The conformation of the ring G is between E1 and 5T1. The benzene ring H is planar. The structure was solved by direct methods and refined anisotropically to the final R value of 0.078 for 4219 statistically significant observed reflections [I o 1.96s(I)]. The absolute chirality was determined based on anomalous dispersion as: C4 (R), C8 (R), C6 (R), C17 (R), C25 (S), C24 (S), C19 (S).

Chez tous les eucaryotes, il existe trois formes distinctes d'ARN polymérase nucléaire (polI, II et III), chacune spécialisée dans la transcription d'une classe de gènes et constituée de plus d'une dizaine de sous-unités. Chez S. Cerevisiae, la Pol III, qui synthétise des petits ARNs stables et non traduits (ARNt, ARNr 5S. . . ), est composée de 17 sous-unités. L'assemblage séquentiel sur le promoteur des facteurs d'initiation TFIIIC et TFIIIB (complexe de pré-initiation), suivi du recrutement de la Pol III, représente la première étape de la transcription des gènes de classe III. Dans ce travail, nous caractérisons un polypeptide de 17 kDa associé à la Pol III comme une nouvelle sous-unité de la Pol III essentielle à la viabilité cellulaire et paralogue aux sous-unités A14 (Pol I) et Rpb4 (Pol II). Les sous-unités C17 et C25 forment un hétérodimère stable, semblable aux paires A43-A14 (Pol I) et Rpb7-Rpb4 (Pol II). Nous démontrons que cet hétérodimère est conservé à travers l'évolution avec l'homologue archébactérien RpoF-RpoE. Nous proposons que le couple C17-C25 intervient lors du recrutement de la Pol III au complexe de pré-initiation, via une interaction entre C17 et la sous-unité Brf1 du facteur d'initiation TFIIIB. Par ailleurs, l'identification de nombreux orthologues de C17 révèle une conservation fonctionnelle de cette sous-unité. Nous démontrons ainsi que la protéine orthologue CGRP-RCP, décrite chez les mammifères comme un transducteur de signal, est une sous-unité de la Pol III humaine. L'existence d'un ancêtre commun d'ARN polymérase simplifie notre vision sur l'évolution moléculaire de ces enzymes. Cette étude représente aussi le premier exemple de sous-unité d'ARN polymérase ayant acquis chez les mammifères une fonction additionnelle, indépendante de la transcription
In all eukaryotes, there are three different forms of RNA polymerase (Pol I, II and III), each specialized in the transcription of one class of genes, and composed of more than ten subunits. In S. Cerevisiae, Pol III that synthesizes small and stable untranslated RNA (tRNA, rRNA 5S. . . ) contains 17 subunits. The sequential assembly of initiation factors TFIIIB and TFIIIC on the promoter (pre-initiation complex), followed by Pol III recruitment, is the first step of the transcription of class III genes. In this study, we characterize a polypeptide of 17 kDa associated with Pol III as a new Pol III subunit essential for cell viability and paralog of A14 (Pol I) and Rpb4 (Pol II) subunits. The subunits C17 and C25 form a stable heterodimer, counterpart of the A43-A14 (Pol I) and the Rpb7-Rpb4 (Pol II) pairs. We demonstrate that this heterodimer is conserved throughout evolution with RpoF-RpoE archaeal homolog. We propose that the C17-C25 couple is required for Pol III recruitment at pre-initiation complex, via the interaction between C17 and Brfl, a subunit of the initiation factor TFIIIB. Additionally, the identification of several orthologs of C17 reveals a functional conservation of this subunit. We demonstrate that the ortholog protein CGRP-RCP, described in mammals as a signal transductor, is a guenine human Pol III subunit. The existence of a common ancestor of RNA polymerase simplifies our vision of the molecular evolution of these enzymes. This study represents also the first example of a RNA polymerase subunit that acquired a dual function in mammals, unrelated to transcription