Journal articles on the topic 'Stress Granule PB'

Tethered interactions between the endoplasmic reticulum (ER) and other membrane-bound organelles allow for efficient transfer of ions and/or macromolecules and provide a platform for organelle fission. Here, we describe an unconventional interface between membraneless ribonucleoprotein granules, such as processing bodies (P-bodies, or PBs) and stress granules, and the ER membrane. We found that PBs are tethered at molecular distances to the ER in human cells in a tunable fashion. ER-PB contact and PB biogenesis were modulated by altering PB composition, ER shape, or ER translational capacity. Furthermore, ER contact sites defined the position where PB and stress granule fission occurs. We thus suggest that the ER plays a fundamental role in regulating the assembly and disassembly of membraneless organelles.

G3BP1, a target of TDP-43, is required for normal stress granule (SG) assembly, but the functional consequences of failed SG assembly remain unknown. Here, using both transformed cell lines and primary neurons, we investigated the functional impact of this disruption in SG dynamics. While stress-induced translational repression and recruitment of key SG proteins was undisturbed, depletion of G3BP1 or its upstream regulator TDP-43 disturbed normal interactions between SGs and processing bodies (PBs). This was concomitant with decreased SG size, reduced SG–PB docking, and impaired preservation of polyadenylated mRNA. Reintroduction of G3BP1 alone was sufficient to rescue all of these phenotypes, indicating that G3BP1 is essential for normal SG–PB interactions and SG function.

Stress granules (SGs) are hypothesized to facilitate TAR DNA-binding protein 43 (TDP-43) cytoplasmic mislocalization and aggregation, which may underly amyotrophic lateral sclerosis pathology. However, much data for this hypothesis is indirect. Additionally, whether P-bodies (PBs; related mRNA-protein granules) affect TDP-43 phenotypes is unclear. Here, we determine that induction of TDP-43 expression in yeast results in the accumulation of SG-like foci that in >90% of cases become the sites where TDP-43 cytoplasmic foci first appear. Later, TDP-43 foci associate less with SGs and more with PBs, though independent TDP-43 foci also accumulate. However, depleting or over-expressing yeast SG and PB proteins reveals no consistent trend between SG or PB assembly and TDP-43 foci formation, toxicity or protein abundance. In human cells, immunostaining endogenous TDP-43 with different TDP-43 antibodies reveals distinct localization and aggregation behaviors. Following acute arsenite stress, all phospho-TDP-43 foci colocalize with SGs. Interestingly, in SG assembly mutant cells (G3BP1/2ΔΔ), TDP-43 is enriched in nucleoli. Finally, formation of TDP-43 cytoplasmic foci following low-dose chronic arsenite stress is impaired, but not completely blocked, in G3BP1/2ΔΔ cells. Collectively, our data suggest that SG and PB assembly may facilitate TDP-43 cytoplasmic localization and aggregation but are likely not essential for these events.

Nesprins are a multi-isomeric family of spectrin-repeat (SR) proteins, predominantly known as nuclear envelope scaffolds. However, isoforms that function beyond the nuclear envelope remain poorly examined. Here, we characterize p50Nesp1, a 50-kD isoform that localizes to processing bodies (PBs), where it acts as a microtubule-associated protein capable of linking mRNP complexes to microtubules. Overexpression of dominant-negative p50Nesp1 caused Rck/p54, but not GW182, displacement from microtubules, resulting in reduced PB movement and cross talk with stress granules (SGs). These cells disassembled canonical SGs induced by sodium arsenite, but not those induced by hydrogen peroxide, leading to cell death and revealing PB–microtubule attachment is required for hydrogen peroxide-induced SG anti-apoptotic functions. Furthermore, p50Nesp1 was required for miRNA-mediated silencing and interacted with core miRISC silencers Ago2 and Rck/p54 in an RNA-dependent manner and with GW182 in a microtubule-dependent manner. These data identify p50Nesp1 as a multi-functional PB component and microtubule scaffold necessary for RNA granule dynamics and provides evidence for PB and SG micro-heterogeneity.

The c-Jun N-terminal kinase (JNK) is part of a mitogen-activated protein kinase (MAPK) signaling cascade. Scaffold proteins simultaneously associate with various components of the MAPK signaling pathway and play a role in signal transmission and regulation. Here we describe the identification of a novel scaffold JNK-binding protein, WDR62, with no sequence homology to any of the known scaffold proteins. WDR62 is a ubiquitously expressed heat-sensitive 175-kDa protein that specifically associates with JNK but not with ERK and p38. Association between WDR62 and JNKs occurs in the absence and after either transient or persistent stimuli. WDR62 potentiates JNK kinase activity; however it inhibits AP-1 transcription through recruitment of JNK to a nonnuclear compartment. HEK-293T cells transfected with WDR62 display cytoplasmic granular localization. Overexpression of stress granule (SG) resident proteins results in the recruitment of endogenous WDR62 and activated JNK to SG. In addition, cell treatment with arsenite results in recruitment of WDR62 to SG and activated JNK to processing bodies (PB). JNK inhibition results in reduced number and size of SG and reduced size of PB. Collectively, we propose that JNK and WDR62 may regulate the dynamic interplay between polysomes SG and PB, thereby mediating mRNA fate after stress.

Lead (Pb) is a widely spread pollutant and leads to diverse morphological and structural changes in the plants. In this study, alleviating role of 5-aminolevulinic acid (ALA) in oilseed rape (Brassica napusL.) was investigated with or without foliar application of ALA (25 mg L−1) in hydroponic environment under different Pb levels (0, 100, and 400 µM). Outcomes stated that plant morphology and photosynthetic attributes were reduced under the application of Pb alone. However, ALA application significantly increased the plant growth and photosynthetic parameters under Pb toxicity. Moreover, ALA also lowered the Pb concentration in shoots and roots under Pb toxicity. The microscopic studies depicted that exogenously applied ALA ameliorated the Pb stress and significantly improved the cell ultrastructures. After application of ALA under Pb stress, mesophyll cell had well-developed nucleus and chloroplast having a number of starch granules. Moreover, micrographs illustrated that root tip cell contained well-developed nucleus, a number of mitochondria, and golgi bodies. These results proposed that under 15-day Pb-induced stress, ALA improved the plant growth, chlorophyll content, photosynthetic parameters, and ultrastructural modifications in leaf mesophyll and root tip cells of theB. napusplants.

Abstract Cellular non-membranous RNA-granules, P-bodies (RNA processing bodies, PB) and stress granules (SG), are important components of the innate immune response to virus invasion. Mechanisms governing how a virus modulates PB formation remain elusive. Here, we report the important roles of GW182 and DDX6, but not Dicer, Ago2 and DCP1A, in PB formation, and that Kaposi’s sarcoma-associated herpesvirus (KSHV) lytic infection reduces PB formation through several specific interactions with viral RNA-binding protein ORF57. The wild-type ORF57, but not its N-terminal dysfunctional mutant, inhibits PB formation by interacting with the N-terminal GW-domain of GW182 and the N-terminal domain of Ago2, two major components of PB. KSHV ORF57 also induces nuclear Ago2 speckles. Homologous HSV-1 ICP27, but not EBV EB2, shares this conserved inhibitory function with KSHV ORF57. By using time-lapse confocal microscopy of HeLa cells co-expressing GFP-tagged GW182, we demonstrated that viral ORF57 inhibits primarily the scaffolding of GW182 at the initial stage of PB formation. Consistently, KSHV-infected iSLK/Bac16 cells with reduced GW182 expression produced far fewer PB and SG, but 100-fold higher titer of infectious KSHV virions when compared to cells with normal GW182 expression. Altogether, our data provide the first evidence that a DNA virus evades host innate immunity by encoding an RNA-binding protein that promotes its replication by blocking PB formation.

Stress granules (SGs) are cytoplasmic aggregates of stalled translational preinitiation complexes that accumulate during stress. GW bodies/processing bodies (PBs) are distinct cytoplasmic sites of mRNA degradation. In this study, we show that SGs and PBs are spatially, compositionally, and functionally linked. SGs and PBs are induced by stress, but SG assembly requires eIF2α phosphorylation, whereas PB assembly does not. They are also dispersed by inhibitors of translational elongation and share several protein components, including Fas-activated serine/threonine phosphoprotein, XRN1, eIF4E, and tristetraprolin (TTP). In contrast, eIF3, G3BP, eIF4G, and PABP-1 are restricted to SGs, whereas DCP1a and 2 are confined to PBs. SGs and PBs also can harbor the same species of mRNA and physically associate with one another in vivo, an interaction that is promoted by the related mRNA decay factors TTP and BRF1. We propose that mRNA released from disassembled polysomes is sorted and remodeled at SGs, from which selected transcripts are delivered to PBs for degradation.

Nesprins are highly conserved spectrin repeat–containing scaffold proteins predominantly known to function at the nuclear envelope (NE). However, nesprin isoforms are emerging with localizations and scaffolding functions at sites away from the NE, suggesting their functions are more diverse than originally thought. In this study, we combined nesprin-1 coimmunoprecipitations with mass spectrometry to identify novel nesprin-1 binding partners for isoforms that localize to subcellular compartments beyond the NE. We show that one of these interactors, matrin-3 (matr3), localizes to mRNA processing bodies (PBs), where we have previously shown a nesprin-1 isoform to localize. Furthermore, we show that Matr3 is part of PB mRNP complexes, is a regulator of miRNA-mediated gene silencing, and possibly shuttles to stress granules in stressed cells. More importantly, we identify a new C-terminally truncated Matr3 isoform that is likely to be involved in these functions and PB localization. This study highlights several novel nesprin-1 binding partners and a new function and localization for Matr3 in cytoplasmic RNA granules.

Exported mRNAs are targeted for translation or can undergo degradation by several decay mechanisms. The 5′→3′ degradation machinery localizes to cytoplasmic P bodies (PBs). We followed the dynamic properties of PBs in vivo and investigated the mechanism by which PBs scan the cytoplasm. Using proteins of the decapping machinery, we asked whether PBs actively scan the cytoplasm or whether a diffusion-based mechanism is sufficient. Live-cell imaging showed that PBs were anchored mainly to microtubules. Quantitative single-particle tracking demonstrated that most PBs exhibited spatially confined motion dependent on microtubule motion, whereas stationary PB pairs were identified at the centrosome. Some PBs translocated in long-range movements on microtubules. PB mobility was compared with mitochondria, endoplasmic reticulum, peroxisomes, SMN bodies, and stress granules, and diffusion coefficients were calculated. Disruption of the microtubule network caused a significant reduction in PB mobility together with an induction of PB assembly. However, FRAP measurements showed that the dynamic flux of assembled PB components was not affected by such treatments. FRAP analysis showed that the decapping enzyme Dcp2 is a nondynamic PB core protein, whereas Dcp1 proteins continuously exchanged with the cytoplasm. This study reveals the mechanism of PB transport, and it demonstrates how PB assembly and disassembly integrate with the presence of an intact cytoskeleton.

Yeast Ssd1 is an RNA-binding protein that shuttles between the nucleus and cytoplasm. Ssd1 interacts with its target mRNAs initially during transcription by binding through its N-terminal prion-like domain (PLD) to the C-terminal domain of RNA polymerase II. Ssd1 subsequently targets mRNAs acquired in the nucleus either to daughter cells for translation or to stress granules (SGs) and P-bodies (PBs) for mRNA storage or decay. Here we show that PB components assist in the nuclear export of Ssd1and subsequent targeting of Ssd1 to PB sites in the cytoplasm. In the absence of import into the nucleus, Ssd1 fails to associate with PBs in the cytoplasm but rather is targeted to cytosolic insoluble protein deposits (IPODs). The association of Ssd1 either with IPOD sites or with PB/SG requires the PLD, whose activity is differentially regulated by the Ndr/LATS family kinase, Cbk1: phosphorylation suppresses PB/SG association but enhances IPOD formation. This regulation likely accrues from a phosphorylation-sensitive nuclear localization sequence located in the PLD. The results presented here may inform our understanding of aggregate formation by RBP in certain neurological diseases.

In mammalian cells, nontranslating messenger RNAs (mRNAs) are concentrated in different cytoplasmic foci, such as processing bodies (PBs) and stress granules (SGs), where they are either degraded or stored. In the present study, we have thoroughly characterized cytoplasmic foci, hereafter called AGs for ALK granules that form in transformed cells expressing the constitutively active anaplastic lymphoma kinase (ALK). AGs contain polyadenylated mRNAs and a unique combination of several RNA binding proteins that so far has not been described in mammalian foci, including AUF1, HuR, and the poly (A+) binding protein PABP. AGs shelter neither components of the mRNA degradation machinery present in PBs nor known markers of SGs, such as translation initiation factors or TIA/TIAR, showing that they are distinct from PBs or SGs. AGs and PBs, however, both move on microtubules with similar dynamics and frequently establish close contacts. In addition, in conditions in which mRNA metabolism is perturbed, AGs concentrate PB components with the noticeable exception of the 5′ to 3′ exonuclease XRN1. Altogether, we show that AGs constitute novel mRNA-containing cytoplasmic foci and we propose that they could protect translatable mRNAs from degradation, contributing thus to ALK-mediated oncogenicity.

Isolite is a ceramic-like, porous soil amendment purported to sustain plant growth under reduced irrigation and increase plant survival during drought. The purpose of this greenhouse experiment was to determine the effect of an Isotite-amended soilless container medium on: (1) growth under reduced irrigation frequency and (2) water stress during drought of Impatiens × hybrids `Accent Red'. On 2 June 1993, seedlings were transplanted into 13.2 liter black plastic pots containing a 4:1 composted pine bark:coarse sand (vol.) medium amended with Isolite CG-1 granules at rates of 0%, 10%, 15%, and 20% (vol.). Study I. Seedlings were. irrigated with 500 ml tap water every two days for two weeks followed by a 4 week schedule of 500 ml tap water every 1, 2, 3, 4, or 5 days. In general, growth parameters were explained by irrigation treatment effects and did not differ with Isolite rate. Growth indices ranged from +54% to + 143%, while final visual quality grades ranged from 2.4 to 5.0 (5-point scale), shoot dry weight from 8.7 to 30.7 g, root dry weight from 2.0 to 7.9 g, and leaf area from 0.14 to 0.48 m2. Study II. Seedlings were irrigated with 500 ml tap water every 2 days for rive weeks followed by a two week drought. Plant water status parameters were similar at all rates of Isolite. Leaf expansion rates ranged from + 89% to +98%, white a final mid-day xylem pressure potential of -0.4 MPa and a final visual quality grade of 2.0 were uniform across all treatments. Under these conditions, Isolite did not limit water stress of container-grown Impatiens `Accent Red'.

The geological evolution of the eastern Grenville Province can be subdivided into three stages. During the first stage, namely pre-Labradorian (> 1710 Ma) and Labradorian (1710–1600 Ma) events, a continental-marginal basin was created and subsequently destroyed during accretion of a magmatic arc formed over a south-dipping subduction zone. Subduction was short-lived and arrested, leading to a passive continental margin. The second stage addresses events between 1600 and 1230 Ma. The passive margin lasted until 1520 Ma, following which a continental-margin arc was constructed during Pinwarian (1520–1460 Ma) orogenesis. Elsonian (1460–1230 Ma) distal-inboard, mafic and anorthositic magmatism, decreasing in age northward, is explained by funnelled flat subduction, possibly associated with an overridden spreading centre. As the leading edge of the lower plate advanced, it was forced beneath the Paleoproterozoic Torngat orogen root between the Archean Superior and North Atlantic cratons, achieving its limit of penetration by 1290 Ma. Static north-northeast-trending rifting then ensued, with mafic magmatism flanked by felsic products to the north and south. Far-field orogenic effects heralded the third stage, lasting from 1230 to 955 Ma. Until 1180 Ma, the eastern Grenville Province was under the distal, mild influence of Elzevirian orogenesis. From 1180 to 1120 Ma, mafic and anorthositic magmatism occurred, attributed to back-arc tectonism inboard of a post-Elzevirian Laurentian margin. Quiescence then prevailed until Grenvillian (1080–980 Ma) continent–continent collision. Grenvillian orogenesis peaked in different places at different times as thrusting released stress, thereby precipitating its shift elsewhere (pressure-point orogenesis). High-grade metamorphism, thrusting and minor magmatism characterized the Exterior Thrust Zone, in contrast to voluminous magmatism in the Interior Magmatic Belt. Following final deformation, early posttectonic anorthositic–alkalic–mafic magmatism (985–975 Ma) and late posttectonic monzonitic–syenite–granite magmatism (975–955 Ma) brought the active geological evolution of this region to a close.

Granitic pegmatite deposits, which are usually products of orogenic processes during plate convergence, can be used to demonstrate regional tectonic evolution processes. In the eastern Tibetan Plateau in China, the Jiajika, Dahongliutan, Xuebaoding, Zhawulong, and Ke’eryin rare metal pegmatite deposits are located in the southern, western, northern, midwestern, and central areas of the Songpan–Ganzê orogenic belt, respectively. In this study, we dated two muscovite Ar–Ar ages of 189.4 ± 1.1 Ma and 187.0 ± 1.1 Ma from spodumene pegmatites of the Dahongliutan deposit. We also dated one zircon U-Pb age of 211.6 ± 5.2 Ma from muscovite granite, two muscovite Ar–Ar ages of 179.6 ± 1.0 Ma and 174.3 ± 0.9 Ma, and one columbite–tantalite U-Pb age of 204.5 ± 1.8 Ma from spodumene pegmatites of the Zhawulong deposit. In addition, we dated one muscovite Ar–Ar age of 159.0 ± 1.4 Ma from spodumene pegmatite of the Ke’eryin deposit. Combining these ages and previous studies in chronology, we concluded that the granitic magma in the Jiajika, Xuebaoding, Dahongliutan, Zhawulong, and Ke’eryin deposits intruded into Triassic metaturbidites at approximately 223, 221, 220–217, 212, and 207–205 Ma, respectively, and that the crystallization of the corresponding pegmatite ceased at approximately 199–196, 195–190, 189–187, 180–174, and 159 Ma, respectively. In this study, we demonstrated that the peak in magmatic activity and the final crystallization age of the pegmatite lagged behind one another from the outer areas of the orogeny belt to the inner areas. The pegmatite–parented granitic magmas were sourced from Triassic metaturbidites that were melted by shear heating along the large-scale decollement resulting from Indosinian collisions along the North China block, Qiangtang–Changdu block, and Yangtze block. As a result, the above temporal and spatial regularities indicated that the tectonic–thermal stress resulting from the collisions of three blocks was transferred from the outer areas of the orogenic belt to the inner areas. A large amount of heat and a slow cooling rate at the convergent center of thermal stress in two directions will lead to crystallization and differentiation of magma in the Songpan–Ganzê orogenic belt, forming additional rare metal deposits.

Abstract The Donkieboud Granodiorite pluton forms an extensive intrusion across the border region between South Africa and southeast Namibia. The mesocratic grey, weakly to moderately K-feldspar porphyritic biotite ± hornblende ± orthopyroxene granodiorite represents the most extensive member of the late- to post-tectonic Komsberg Suite (~1 125 to 1 105 Ma) which intruded as sheet-like bodies into the older high grade paragneisses and orthogneisses (~1 230 to 1 140 Ma) of the Kakamas Domain of the Mesoproterozoic Namaqua-Natal Province. The Donkieboud Granodiorite comprises three main textural variations namely:a porphyritic to weakly porphyritic, relatively undeformed rock with randomly orientated ovoid and twinned feldspar phenocrysts;a weakly- to well-foliated gneiss with between 3 to 10% feldspar phenocrysts set in a medium-grained matrix anda patchy metamorphic charnockite variety. Large inclusions of the strongly foliated Twakputs (~1 210 Ma) and the Witwater (~1 140 Ma) garnetiferous granite gneisses occur within the Donkieboud Granodiorite and mafic xenoliths are common. The Donkieboud Granodiorite is variably deformed ranging from unfoliated to being gneissic. The foliation developed during its intrusion into an existing but waning regional stress field with the strain increasing towards the contacts with the surrounding country rocks. Subsequent km-scale open folding resulted in the reorientation of the gneissic foliation and locally, intense reworking of the fabrics along the margins of the folds. In places, the Donkieboud unit is crosscut by discrete mylonitic shears with a west to northwest trend. U-Pb zircon dating of the Donkieboud Granodiorite samples yielded concordia ages of between 1 118 and 1 107 Ma. Overall the Donkieboud Granodiorite has an intermediate to felsic composition (mean SiO2: 63.9 ± 2.2 wt.%) and is strongly metaluminous. This, together with its biotite-hornblende ± orthopyroxene mineral assemblage and the abundance of mafic xenoliths, suggests it is an I-type granitoid, with the source magma produced by partial melting of older igneous rocks that had not undergone any significant amount of chemical weathering. The εNd values of -1.15 and -0.11 and TDM values of 1 615 and 1 505 Ma are typical of the Komsberg Suite and indicate a significant contribution of older crustal material to the magma of the Donkieboud pluton.

The present volume marks the completion of a large research project by the Geological Survey of Denmark and Greenland (GEUS), focused on the northern part of the Palaeoproterozoic Nagssugtoqidian orogen of central West Greenland, and carried out by a team of Danish and international participants. The project comprised geological mapping as well as structural, geochronological, geochemical and economic geological studies. This volume contains reports on both Archaean and Palaeoproterozoic geology as well as a study of neotectonic brittle structures. The field work was carried out in 2000-2003 in the region between Nordre Strømfjord and Jakobshavn Isfjord (see e.g. van Gool & Piazolo 2006, this volume, fig. 1). The project had two immediate purposes, namely to establish an overview of the mineral resource potential of supracrustal rocks in the region between 66° and 70°15'N, and produce four new geological sheets in the Survey's 1:100 000 map series. The first collection of papers about the Nagssugtoqidian orogen, published by the Geological Survey of Greenland (GGU, now part of GEUS), dates back to 1979 (Korstgård 1979). The investigations in this period were mainly based on field descriptions and structural analysis of coastal areas in the southern and central parts of the orogen, combined with limited petrographical, palaeomagnetic and geochronological studies; the results also comprised the first 1:100 000 geological map from within the Nagssugtoqidian orogen (Olesen 1984). The Proterozoic age of the orogen had been established, but it was believed that most, if not all of the quartzofeldspathic basement gneisses were of Archaean origin. Subsequent work in the Nagssugtoqidian orogen by GGU in the 1980s showed that besides Archaean orthogneisses and supracrustal rocks, the central part of the orogen also comprises the root zone of a Palaeoproterozoic magmatic arc and associated panels of Palaeoproterozoic volcanic and metasedimentary rocks (Kalsbeek et al. 1987). These results were confirmed during further investigations by the Danish Lithosphere Centre (DLC) in 1994-1999, and the plate-tectonic collisional history of the southern and central Nagssugtoqidian orogen was described in detail (van Gool et al. 2002). However, these studies added little to previous knowledge of the northern parts of the orogen in the Kangaatsiaq-Aasiaat-Qasigiannguit region, knowledge that was largely based on coastal reconnaissance by Henderson (1969) at the time when the entire orogen was still believed to consist of Archaean rocks. Another project preceding the present work was carried out by GGU in 1988-1991 immediately north of the Nagssugtoqidian orogen, in the southernmost part of the likewise Palaeoproterozoic Rinkian fold belt (Disko Bugt project, Kalsbeek 1999). It was shown that also the latter region comprises Palaeoproterozoic (meta)sedimentary rocks, and that most of the Archaean basement is strongly overprinted by Palaeoproterozoic structures that were formed during overall W- or NW-directed lateral tectonic transport. Although these structures might be related to similar structures in the Nagssugtoqidian orogen, the relationship between the Nagssugtoqidian orogen and the Rinkian fold belt remained speculative. The only previous economic geological study of regional extent in central West Greenland was an airborne reconnaissance study supplemented by local field work, which was carried out in the early 1960s by Kryolitselskabet Øresund A/S. This work resulted in the discovery of a massive sulphide deposit at Naternaq (Lersletten), which was studied again in some detail in 2001 by the Survey (Østergaard et al. 2002) but not reported on in the present volume. The present volume comprises 12 papers with topics ranging geochronologically from mid-Archaean to Palaeogene, and geographically from the southern Nagssugtoqidian foreland to the central part of the Rinkian fold belt. Many of the papers deal with the northern part of the Nagssugtoqidian orogen and are related to the recent field work in that region, while a few contributions are rooted in DLC- or other projects. The papers have been arranged in approximate chronological order and are grouped in terms of their main subjects. The two first papers, by Hollis et al. and Moyen & Watt, deal with Archaean supra- and infracrustal rocks in the northern Nagssugtoqidian orogen: their origin, ages, and structural and metamorphic evolution. These papers provide insight into the age and origin of the continental crustal orthogneisses and granites that underlie most of the region, and discuss the relationships between the supracrustal and plutonic components, using zircon U-Pb age determinations and major and trace element geochemical characteristics. Also the question of Palaeoproterozoic tectonic overprint is discussed, with the conclusion from both study areas that most of the observed structures are Archaean. The third paper with focus on Archaean geology, by Stendal et al., describes a small gold prospect at Attu likewise in the northern Nagssugtoqidian orogen, and discusses the age of the prospect and its host rocks using Pb-Pb geochronology of magnetite. It is concluded that the host rocks at Attu may be as old as 3162 ± 43 Ma, and that the gold prospect itself is around 2650 Ma in age. The fourth paper, by Mayborn & Lesher, is a thorough review of the Kangâmiut dyke swarm in the southern Nagssugtoqidian orogen and its foreland. It includes new whole-rock and mineral chemical data, and a list of sampling sites and corresponding field data. The emplacement mechanism and depth of the dyke swarm are discussed in detail, and it is concluded that the dykes were emplaced during the initial rifting prior to the Nagssugtoqidian collision and that they are unrelated to subduction processes (contrary to the belief by some previous authors). The next three papers provide geochronological constraints on the ages of supra- and infracrustal rocks and the deformation and metamorphism in the northern Nagssugtoqidian orogen, and on late orogenic uplift in the central Rinkian fold belt. In the first of these papers Thrane & Connelly employ zircon U-Pb age determinations (mainly using the laser ICP-MS method), and for the first time provide unequivocal documentation that the Naternaq supracrustal belt is of Palaeoproterozoic age. Other zircon age data from a synkinematic granite southeast of Kangaatsiaq show that the large fold structures in this region are of Archaean age. The subsequent paper by Stendal et al. presents Pb-Pb ages and isotopic signatures of magnetite in amphibolites; the obtained ages are younger than 1800 Ma and are related to cooling of the orogen. Stepwise leaching Pb-Pb ages of monazite and allanite in pegmatites fall in the range of 1750-1800 Ma, and are interpreted to date the emplacement of these rocks. The third paper in this group, by Sidgren et al., deals with new 40Ar/39Ar ages of around 1790 Ma (hornblende) and 1680 Ma (muscovite) from Archaean and Palaeoproterozoic rocks in the central Rinkian fold belt, which are interpreted as orogenic cooling ages. The hornblende ages are significantly older than such hornblende ages previously obtained from the central and northern Nagssugtoqidian orogen, pointing to different uplift histories in the two regions. This may in turn suggest that the Rinkian continental collision preceded that in the Nagssugtoqidian orogen. Four of the remaining five papers deal with the Nagssugtoqidian structural evolution. In the first of these, van Gool & Piazolo present a new method of structural analysis, where a geographical information system (GIS) is used as a framework for visualisation and analysis of large amounts of structural data. The paper graphically presents an overview of thousands of data points within an area of approximately 160 × 180 km in the central and northern parts of the Nagssugtoqidian orogen. This interesting data set points directly towards the two next papers, where crustal-scale structures in the same region and their origin are discussed: Sørensen et al. address the prominent Nordre Strømfjord shear zone just south of this block, and describes the structural and metasomatic transition into the shear zone by means of aeromagnetic and lithological map patterns and geochemical data. Another paper, by Mazur et al., addresses a prominent break in the structural pattern within the Kangaatsiaq-Aasiaat area, where the southern part acted as a rigid block during the Nagssugtoqidian orogeny and thus preserved its Archaean structure. The fourth paper in this group, by Korstgård et al., combines rock and aeromagnetic data to discuss the relationship between structure, metamorphic facies and total magnetic field intensity anomalies in the southern Nagssugtoqidian orogen. The authors show that static metamorphic boundaries are gradual, whereas boundaries along deformation zones are abrupt. The last paper, by Wilson et al., is a novel remote sensing and field geological analysis of onshore brittle structures related to the complex Ungava fault zone in the Davis Strait, which developed during the Cretaceous-Palaeogene opening of the Labrador Sea - Davis Strait - Baffin Bay seaway. The study area is located in the central Nagssugtoqidian orogen, and the authors carefully establish a distinction between old Nagssugtoqidian and younger structures in the basement rocks and identify five main sets of young lineaments. They conclude that the onshore fault patterns are predominantly of strike-slip nature, and that they reflect the stress fields that governed the opening of the seaway. Acknowledgements The editors are grateful to the 14 external reviewers, each of whom reviewed one or more of the individual papers, for their thorough and constructive work.

ABSTRACT Stress granules (SGs) are cytoplasmic aggregates formed upon stress when untranslated messenger ribonucleoproteins accumulate in the cells. In a green fluorescent protein library screening of the fission yeast SG proteins, Puf2 of the PUF family of RNA-binding proteins was identified that is required for SG formation after deprivation of glucose. Accordingly, the puf2 mutant is defective in recovery from glucose starvation with a much longer lag to reenter the cell cycle. In keeping with these results, Puf2 contains several low-complexity and intrinsically disordered protein regions with a tendency to form aggregates and, when overexpressed, it represses translation to induce aggregation of poly(A) binding protein Pabp, the signature constituent of SGs. Intriguingly, overexpression of Puf2 also enhances the structure of processing bodies (PBs), another type of cytoplasmic RNA granule, a complex of factors involved in mRNA degradation. In this study, we demonstrate a function of the fission yeast PB in SG formation and show Puf2 may provide a link between these two structures.

ABSTRACTRotavirus replicates in unique virus-induced cytoplasmic inclusion bodies called viroplasms (VMs), the composition and structure of which have yet to be understood. Based on the analysis of a few proteins, earlier studies reported that rotavirus infection inhibits stress granule (SG) formation and disrupts P bodies (PBs). However, the recent demonstration that rotavirus infection induces cytoplasmic relocalization and colocalization with VMs of several nuclear hnRNPs and AU-rich element-binding proteins (ARE-BPs), which are known components of SGs and PBs, suggested the possibility of rotavirus-induced remodeling of SGs and PBs, prompting us to analyze a large number of the SG and PB components to understand the status of SGs and PBs in rotavirus-infected cells. Here we demonstrate that rotavirus infection induces molecular triage by selective exclusion of a few proteins of SGs (G3BP1 and ZBP1) and PBs (DDX6, EDC4, and Pan3) and sequestration of the remodeled/atypical cellular organelles, containing the majority of their components, in the VM. The punctate SG and PB structures are seen at about 4 h postinfection (hpi), coinciding with the appearance of small VMs, many of which fuse to form mature large VMs with progression of infection. By use of small interfering RNA (siRNA)-mediated knockdown and/or ectopic overexpression, the majority of the SG and PB components, except for ADAR1, were observed to inhibit viral protein expression and virus growth. In conclusion, this study demonstrates that VMs are highly complex supramolecular structures and that rotavirus employs a novel strategy of sequestration in the VM and harnessing of the remodeled cellular RNA recycling bins to promote its growth.IMPORTANCERotavirus is known to replicate in specialized virus-induced cytoplasmic inclusion bodies called viroplasms (VMs), but the composition and structure of VMs are not yet understood. Here we demonstrate that rotavirus interferes with normal SG and PB assembly but promotes formation of atypical SG-PB structures by selective exclusion of a few components and employs a novel strategy of sequestration of the remodeled SG-PB granules in the VMs to promote virus growth by modulating their negative influence on virus infection. Rotavirus VMs appear to be complex supramolecular structures formed by the union of the triad of viral replication complexes and remodeled SGs and PBs, as well as other host factors, and designed to promote productive virus infection. These observations have implications for the planning of future research with the aim of understanding the structure of the VM, the mechanism of morphogenesis of the virus, and the detailed roles of host proteins in rotavirus biology.

During reaction to stress caused by viral infection, RNA granules are formed in order to protect mRNA. Stress granules (SG) and processing bodies (PB) provide cell homeostasis and mRNA stability. They are formed, for example, during polio virus and MRV (mammalian orthoreovirus) infections. Some viruses, such as influenza virus and HTLV-1 (Human T-lymphotropic virus 1), block the formation of granules. In addition, there are viruses like West Nile Virus, Hepatitis C Virus (HCV) or human Herpes viruses, which influence the functioning of the granules.

Processing bodies (PBs) are ribonucleoprotein granules important for cytokine mRNA decay that are targeted for disassembly by many viruses. Kaposi’s sarcoma-associated herpesvirus is the etiological agent of the inflammatory endothelial cancer, Kaposi’s sarcoma, and a PB-regulating virus. The virus encodes Kaposin B (KapB), which induces actin stress fibres (SFs) and cell spindling as well as PB disassembly. We now show that KapB-mediated PB disassembly requires actin rearrangements, RhoA effectors and the mechanoresponsive transcription activator, YAP. Moreover, ectopic expression of active YAP or exposure of ECs to mechanical forces caused PB disassembly in the absence of KapB. We propose that the viral protein KapB activates a mechanoresponsive signaling axis and links changes in cell shape and cytoskeletal structures to enhanced inflammatory molecule expression using PB disassembly. Our work implies that cytoskeletal changes in other pathologies may similarly impact the inflammatory environment.

The widespread Early Cretaceous plutons intruding along the southern Great Xing’an Range (SGXR) provide evidence for tectonic evolution of the region. Petrological, geochemical, zircon U–Pb geochronology and zircon Hf isotopic studies are conducted on intrusions from Bianjiadayuan and Hongling areas. These suites classify as A2-type granites and monzodiorites, respectively. The 138–133 Ma A2-type granites originated from partial melting of continental crustal materials at high temperatures and shallow depths with significant addition of juvenile mafic lower crust sourced from a metasomatized mantle. The 136–134 Ma monzodiorites originated from the partial melting of an enriched mantle that was modified by melts of a previously subducted slab coupled with crustal contamination. The Early Cretaceous magmatism in the SGXR occurred in two periods: ∼145–136 Ma (peak at ∼139 Ma; εHf (t) = 5 to 10) and ∼136–130 Ma (peak at ∼131 Ma; εHf (t) = −10 to 15). The Early Cretaceous granite–monzodiorite suite in the SGXR suggests a bimodal magmatism in an extensional setting. The ∼145–130 Ma magmatism may have been triggered by asthenospheric upwelling induced by the Mongol–Okhotsk oceanic slab breakoff and large-scale lithospheric delamination resulting from post-orogenic extension. The variation of subduction direction of the Paleo-Pacific Ocean likely triggered a change in stress regime at ca. 136 Ma and likely promoted the lithospheric delamination beneath the SGXR resulting in intense magmatism originating from various sources. As such, the Paleo-Pacific Oceanic subduction likely played an important role in the Early Cretaceous magmatism in the SGXR.