Biology subjects

Singh, A.

Publications and source records attributed to Singh, A..

At least 505 records · Page 28Linked to original sources

bioRxiv2021

The phenotypic landscape of essential human genes

Understanding the basis for cellular growth, proliferation, and function requires determining the contributions of essential genes to diverse cellular processes. Here, we combined pooled CRISPR/Cas9-based functional screening of 5,072 fitness-conferring genes in human cells with microscopy-based visualization of DNA, DNA damage, actin, and microtubules. Analysis of >31 million individual cells revealed measurable phenotypes for >90% of genes. Using multi-dimensional clustering based on hundreds of quantitative phenotypic parameters, we identified co-functional genes across diverse cellular activities, revealing novel gene functions and associations. Pooled live-cell screening of [~]450,000 cell division events for 239 genes further identified functional contributions to chromosome segregation. Our work creates a resource for the phenotypic analysis of core cellular processes and defines the functional landscape of essential human genes.

cell biology↗

bioRxiv2021

Recurrent evolution of cross-resistance in response to selection for improved post-infection survival in Drosophila melanogaster

The host susceptibility to one pathogen can decrease, increase, or remain unaffected by virtue of the host evolving resistance towards a second pathogen. Negative correlations between a host susceptibility to different pathogens is an often-cited explanation for maintenance of genetic variation in immune function determining traits in a host population. In this study, we investigated the change in susceptibility of Drosophila melanogaster flies to various novel bacterial pathogens after being experimentally selected for increased resistance to one particular bacterial pathogen. We independently selected flies to become more resistant towards Enterococcus faecalis and Pseudomonas entomophila, and baring a few exceptions the evolved populations exhibited cross-resistance against the range of pathogens tested in the study. Neither the identity of the native pathogen nor the host sex was major determining factors in predicting the pattern of cross-resistance exhibited by the selected populations. We therefore report that a generalized cross-resistance to novel pathogens can repeatedly evolve in response to selection for resistance against a single pathogen.

evolutionary biology↗

bioRxiv2021

REDigest: a Python GUI for In-Silico Restriction Digestion Analysis of Genes or Complete Genome Sequences

Restriction fragment length polymorphism (RFLP) is a technology for the molecular characterization of DNA and widely used genome mapping, medical genetics, molecular microbiology and forensics etc. Terminal restriction fragment length polymorphism (T-RFLP), a variant of RFLP is extensively used in environmental microbiology for the microbial community profiling based on the restriction digestion profile of marker gene (16S rRNA, FTHFS etc.) amplicons. At present, there is a lack of a tool which can perform in-silico restriction digestion of a large number of sequences at a time, in an interactive way and as an output produce sequences of the restriction fragments and visualization plot. I have developed a graphical user interface based software "REDigest" for the in-silico restriction digestion analysis for gene or genome sequences. The REDigest software program with a graphical user interface is freely available at https://github.com/abhijeetsingh1704/REDigest.

bioinformatics↗

bioRxiv2021

Identification of mRNAs that undergo stop codon readthrough in Arabidopsis thaliana

A stop codon ensures termination of translation at a specific position on an mRNA. Sometimes, termination fails as translation machinery recognizes a stop codon as a sense codon. This leads to stop codon readthrough (SCR) resulting in the continuation of translation beyond the stop codon, generating protein isoforms with C-terminal extension. SCR has been observed in viruses, fungi, and multicellular organisms including mammals. However, SCR is largely unexplored in plants. In this study, we have analyzed ribosome profiling datasets to identify mRNAs that undergo SCR in Arabidopsis thaliana. Analyses of the ribosome density, ribosome coverage and three-nucleotide periodicity of the ribosome profiling reads, in the mRNA region downstream of the stop codon, provided strong evidence for SCR in mRNAs of 144 genes. This process generates putative peroxisomal targeting signal, nuclear localization signal, prenylation signal, transmembrane helix and intrinsically disordered regions in the C-terminal extension of several of these proteins. Gene ontology (GO) functional enrichment analysis revealed that these 144 genes belong to three major functional groups - translation, photosynthesis and abiotic stress tolerance. Finally, using a luminescence-based assay, we experimentally demonstrate SCR in representative mRNAs belonging to these functional classes. Based on these observations, we propose that SCR plays an important role in plant physiology by regulating the protein localization and function. AUTHOR SUMMARYProtein synthesis executed by macromolecular complexes, termed ribosomes, starts and stops at specific locations on a messenger RNA (mRNA). This fidelity is critical for the normal functioning of cells. However, sometimes ribosomes dont stop translation at the stop signal (termed stop codon) on an mRNA resulting in longer proteins with properties different from those of the canonical shorter protein. This process called stop codon readthrough (SCR) has been observed in viruses, fungi, and multicellular organisms including mammals. However, it remains largely unexplored in plants. In this study, we report evidence of SCR in 144 genes of Arabidopsis thaliana, a small flowering weed widely used as a model system to study plant biology. These genes are involved in protein synthesis, photosynthesis and stress tolerance in plants. We have also experimentally demonstrated SCR in a few genes that represent these functional classes. Our analysis shows that SCR can change the localization and functional properties of these proteins. We propose that SCR plays an important role in plant physiology.

plant biology↗

bioRxiv2021

HIV-specific CD8+ T-cells in tonsils express exhaustive TRM-like signatures

Lymphoid tissues are an important HIV reservoir site that persists in the face of antiretroviral therapy and natural immunity. Targeting these reservoirs by harnessing the antiviral activity of local tissue resident memory ( TRM) CD8+ T-cells is of great interest, but limited data exist on TRMs within lymph nodes of people living with HIV (PLWH). Here, we studied tonsil CD8+ T-cells obtained from PLWH and uninfected controls from South Africa. We show that these cells are preferentially located outside the germinal centers (GCs), the main reservoir site for HIV, and display a low cytolytic and transcriptionally TRM-like profile that is distinct from blood. In PLWH, CD8+ TRM-like cells are highly expanded and adopt a more cytolytic, activated and exhausted phenotype characterized by increased expression of CD69, PD-1 and perforin, but reduced CD127. This phenotype was enhanced in HIV-specific CD8+ T-cells from tonsils compared to matched blood. Single-cell profiling of these cells revealed a clear transcriptional signature of T-cell activation, clonal expansion and exhaustion ex-vivo. In contrast, this signature was absent from HIV-specific CD8+ T-cells in tonsils isolated from a natural HIV controller, who expressed lower levels of cell surface PD-1 and CXCR5, and reduced transcriptional evidence of T-cell activation, exhaustion and cytolytic activity. Thus, we show that HIV-specific TRM-like CD8+ T-cells in tonsils from non-HIV controllers are enriched for activation and exhaustion profiles compared to those in blood, suggesting that lymphoid HIV-specific CD8+ TRM cells are potentially ideal candidates for immunotherapy to modulate their ability to targeting the HIV reservoirs.

immunology↗

bioRxiv2021

Cholesterol and sphingomyelin are critical for Fcγ receptor-mediated phagocytosis of Cryptococcus neoformans by macrophages

Cryptococcus neoformans is a fungal pathogen that causes life-threatening meningoencephalitis in lymphopenic patients. Pulmonary macrophages comprise the first line of host defense upon inhalation of fungal spores, whereby macrophages either aid in clearance or serve as a niche for its dissemination. Given that macrophages play a key role in the outcome of a cryptococcal infection, it is crucial to understand factors that mediate phagocytosis of C. neoformans. Since lipid rafts (high order plasma membrane domains enriched in cholesterol and sphingomyelin) have been implicated in facilitating phagocytosis, we evaluated whether these ordered domains govern macrophages ability to phagocytose C. neoformans. We found that cholesterol or sphingomyelin depletion resulted in significantly deficient IgG-mediated phagocytosis of the fungus. Moreover, repletion of macrophage cells with a raft-promoting sterol (7-dehydrocholesterol) rescued this phagocytic deficiency while a raft-inhibiting sterol (coprostanol) significantly decreased IgG-mediated phagocytosis of C. neoformans. Using a photoswitchable sphingomyelin (AzoSM), we observed that the raft-promoting conformation (trans-AzoSM) resulted in efficient phagocytosis whereas raft-inhibiting conformation (cis-AzoSM) significantly blunted phagocytosis in a reversible manner. We observed that the effect on phagocytosis may be mediated by facilitating Fc{gamma} receptor (Fc{gamma}R) function, whereby IgG immune complexes cross-link to Fc{gamma}RIII, resulting in tyrosine phosphorylation of FcR {gamma}-subunit (FcR{gamma}), an important accessory protein in the Fc{gamma}R signaling cascade. Correspondingly, cholesterol or sphingomyelin depletion resulted in decreased FcR{gamma} phosphorylation. Repletion with 7-dehydrocholesterol restored phosphorylation, whereas repletion with coprostanol showed FcR{gamma} phosphorylation comparable to unstimulated cells. Together, these data suggest that lipid rafts are critical for facilitating Fc{gamma}RIII-mediated phagocytosis of C. neoformans.

microbiology↗

bioRxiv2021

Computational analysis reveals similarities and differences between SCLC subtypes

Small cell lung cancer (SCLC) is a neuroendocrine malignancy with dismal survival rates. Previous studies have revealed inter and intra tumoral heterogeneity of SCLC driven by neuroendocrine differentiation and multiple gene expression signatures have been proposed to classify the distinct SCLC molecular subtypes However, few questions remain unanswered: a) how many SCLC subtypes exist? b) how similar or different are these subtypes?, c) which gene list(s) can be used to identify those specific subtypes? Here, we show that irrespective of the three gene sets (33 genes, 50 genes, 105 genes) proposed in different studies to classify SCLC into different subtypes, the markers of phenotypic heterogeneity in SCLC form a "teams" like pattern of co-expressed modules. Moreover, the 105 geneset could classify SCLC cell lines into five clusters, three of which can be distinctly mapped to the SCLC-A, SCLC-N and SCLC-Y subtypes. Intriguingly, we noticed a high degree of similarity in the transcriptional landscape of two non-neuroendocrine subtypes: SCLC-Y and SCLC-I*, as well as in their enrichment of EMT. Thus, our analysis elucidates the landscape of phenotypic heterogeneity enabling diverse SCLC subtypes.

cancer biology↗

bioRxiv2021

SPARClink: an interactive tool to visualize the impact of the SPARC program

The NIH SPARC program seeks to accelerate the development of therapeutic devices that modulate electrical activity in nerves to improve organ function. SPARC-funded researchers are generating rich datasets from neuromodulation research that are curated and shared according to FAIR (Findable, Accessible, Interoperable, and Reusable) guidelines and are accessible to the public on the SPARC data portal. Keeping track of the utilization of these datasets within the larger research community is a feature that will benefit data generating researchers in showcasing the impact of their SPARC outcomes. This will also allow the SPARC program to display the impact of the FAIR data curation and sharing practices that have been implemented. This manuscript provides the methods and outcomes of SPARClink, our web tool for visualizing the impact of SPARC, which won the 2nd prize at the 2021 SPARC FAIR Codeathon. With SPARClink, we built a system that automatically and continuously finds new published SPARC scientific outputs (datasets, publications, protocols) and the external resources referring to them. SPARC datasets and protocols are queried using publicly accessible REST APIs (provided by Pennsieve and Protocols.io) and stored in a publicly accessible database. Citation information for these resources is retrieved using the NIH reporter API and NCBI Entrez system. A novel knowledge-graph-based structure was created to visualize the results of these queries and showcase the impact that the FAIR data principles can have on the research landscape when they are adopted by a consortium.

bioinformatics↗

bioRxiv2021

A single-cell approach reveals variation in cellular phage-producing capacities

Virus burst size, a component of viral fitness, is the average number of viral particles released from a single infected cell. In this study, we estimated bacteriophage lambda ({lambda}) burst size mean and distribution at different lysis times. To estimate phage {lambda} burst sizes at single-cell level, we employed a lysis-deficient E. coli lysogen, which allowed chemical lysis at desired times after the induction of lytic cycle. Induced cultures of E. coli lysogen were diluted and aliquoted into the wells of 96-well plates. A high dilution rate results in mostly empty wells and minimizes the probability of having multiple cells in wells that do receive cells. Burst size was estimated by titering single-cell lysates obtained after chemical lysis at desired times. Our data shows that the viral burst size initially increases exponentially with the lysis time, and then saturates at longer lysis times. We also demonstrate that cell-to-cell variation or "noise" in lysis timing does not significantly contribute to the burst size noise. The burst size noise remains constant with increasing mean burst size. The most likely explanation for the experimentally observed constant burst size noise is that cell-to-cell differences in burst size originate from differences in cellular capacity to produce phages. The mean burst size measured at different lysis times is positively correlated to cell volume, which may determine the cellular phage production capacity. However, experiments controlling for cell size indicates that there are other factors in addition to cell size that determine this cellular capacity. ARTICLE IMPORTANCEPhages produce offspring by hijacking a cells replicative machinery. Previously, it was noted that the variation in the number of phages produced by single infected cells far exceeded cell size variation. It has been hypothesized that this variation is a consequence of variation in the timing of host cell lysis. Here we show that cell-to-cell variation in lysis timing does not significantly contribute to the burst size variation. We suggest that the constant burst size variation across different host lysis times results from cell-to-cell differences in capacity to produce phages. We find that the mean burst size measured at different lysis times is positively correlated to cell volume, which may determine the cellular phage production capacity. However, experiments controlling for cell size indicates that there are other factors in addition to cell size that determine this cellular capacity.

microbiology↗

bioRxiv2021

Concentration fluctuations due to size-dependent gene expression and cell-size control mechanisms

Intracellular reaction rates depend on concentrations and hence their levels are often regulated. However classical models of stochastic gene expression lack a cell size description and cannot be used to predict noise in concentrations. Here, we construct a model of gene product dynamics that includes a description of cell growth, cell division, size-dependent gene expression, gene dosage compensation, and size control mechanisms that can vary with the cell cycle phase. We obtain expressions for the approximate distributions and power spectra of concentration fluctuations which lead to insight into the emergence of concentration homeostasis. Furthermore, we find that (i) the conditions necessary to suppress cell division-induced concentration oscillations are difficult to achieve; (ii) mRNA concentration and number distributions can have different number of modes; (iii) certain size control strategies are ideal because they maintain constant mean concentrations whilst minimising concentration noise. Predictions are confirmed using lineage data for E. coli, fission yeast and budding yeast.

systems biology↗

bioRxiv2021

Topological Constraints on Noise Propagation in Gene Regulatory Networks

Gene expression, the production of protein from DNA and mRNA in the biological cell, is inherently stochastic. Cells with identical DNA exhibit fluctuations or noise in gene expression. This noise propagates over gene regulatory networks (GRNs), which encode gene-gene interactions. The propagated extrinsic noise interacts and combines with intrinsic noise to affect biological decisions. Consequently, it is essential to understand how GRN topology affects total noise. Recently, uncertainty principles were established for noise propagation over GRN. In particular, in ring GRNs, exactly one node can have noise reduction below the intrinsic limit. We establish necessary and sufficient conditions for noise reduction in ring GRN. Specifically, for two- and three-node rings, an odd number of negative regulations is necessary for noise reduction. Further, sufficiency is ensured if sensitivities to input for feedforward and feedback regulations are bounded from below and above, respectively. These constraints are valid even if the ring GRN are regulated by an upstream gene. Finally, we use graph theory to decompose noise propagation in a general directed network over its strongly connected components. The combination of graph theory and stochastic processes may be a general framework for studying noise propagation.

systems biology↗

bioRxiv2021

Amplification and attenuation of noisy expression by export processes

Inside mammalian cells, single genes are known to be transcribed in stochastic bursts leading to the synthesis of nuclear RNAs that are subsequently exported to the cytoplasm to create mRNAs. We systematically characterize the role of export processes in shaping the extent of random fluctuations (i.e. noise) in the mRNA level of a given gene. Using the method of Partitioning of Poisson arrivals, we derive an exact analytical expression for the noise in mRNA level assuming that the nuclear retention time of each RNA is an independent and identically distributed random variable following an arbitrary distribution. These results confirm recent experimental/theoretical findings that decreasing the nuclear export rate buffers the noise in mRNA level, and counterintuitively, decreasing the noise in the nuclear retention time enhances the noise in the mRNA level. Next, we further generalize the model to consider a dynamic extrinsic disturbance that affects the nuclear-to-cytoplasm export. Our results show that noise in the mRNA level varies non-monotonically with the disturbance timescale. More specifically, high- and low-frequency external disturbances have little impact on the mRNA noise level, while noise is amplified at intermediate frequencies. In summary, our results systematically uncover how the coupling of bursty transcription with nuclear export can both attenuate or amplify noise in mRNA levels depending on the nuclear retention time distribution and the presence of extrinsic fluctuations.

systems biology↗

bioRxiv2021

Avian haemosporidians (Plasmodium and Haemoproteus) in selected bird groups (Old world Flycatchers, Warblers, Babblers, and Thrushes) of India and their phylogenetic relationships with other lineages of the world

The avian haemosporidians (Plasmodium and Haemoproteus) are widely distributed and may affect the host populations from body damage at individual level to the extinction of a population. The knowledge about their status may help in future avifauna conservation plans. Hence, we examined the avian haemosporidians status, in selected bird groups (Old world Flycatchers, Warblers, Babblers, and Thrushes) of India, and their phylogenetic relationships with other known lineages of the world. We used the common genetic marker (Cytochrome b gene fragment of 479 bp) with information on the geographic distribution of parasite and host species available at MalAvi database. The prevalence of avian haemosporidians, from northern, eastern, and southern parts of India and phylogenetic genetic analysis of lineages was carried out to know the genetic relatedness among them at local and world level. The MCC tree revealed six Haemosporidian lineages in which one was common (H_MSP01) and five were unique (H_CYOPOL01, H_CHD01, H_CYORUB01, H_EUMTHA01, and P_GEOCIT01). The avian host richness Index was 2.0852. 9.9%, prevalence of Haemosporidian infection was found in 111 DNA samples belonging to 6 host species. The Haemoproteus prevalence was found to be 9.0 % across five host species (Phylloscopus trochiloides, Cyornis poliogenys, C. hainanus dialilaemus, C. rubeculoides, Eumiyas thalassinus) and Plasmodium prevalence was 0.9% in Geokichla citrina. Spatial phylogeny at global level showed H_MSP01 lineage, found in different host species in India, was genetically related to H. pallidus lineages (COLL2 and PFC1) in parts of Africa, Europe, North America, Malaysia, and Philippines. The Plasmodium lineage (P_GEOCIT01) was related to PADOM16 in Egypt with poor sequence similarity (93.89%). The statistical analysis suggested that the haemosporidians host species distribution range was directly and significantly associated with the altitude, minimum temperature, and relative humidity. H_MSP01 distribution was in accordance with H. pallidus having a wide geographic and host range.

genetics↗

bioRxiv2021

Acetobase: database update and reanalysis offormyltetrahydrofolate synthetase amplicon sequencing data from the anaerobic digesters

AcetoBase is a public repository and database published in 2019, for the formyltetrahydrofolate synthetase (FTHFS) sequences. It is the first systematic collection of bacterial formyltetrahydrofolate nucleotide and protein sequences from the genomes and metagenome assembled genomes (MAGs), as well as sequences generated by clone library sequencing. In addition, AcetoBase was first to establish connection between FTHFS gene with the Wood-Ljungdahl pathway and 16S rRNA genes. Since the publication of AcetoBase, significant improvements were seen in the taxonomy of many bacterial lineages and accessibility/availability of public genomics and metagenomics data. Thus, an update to the AcetoBase database with new sequence data and taxonomy has been made along with improvements in web-functionality and user interface. The update in AcetoBase reference database version 2 was furthermore evaluated by reanalysis of publicly accessible FTHFS amplicon sequencing data previously analysed with AcetoBase version 1. The latest database update showed significant improvements in the taxonomic assignments of FTHFS sequences. AcetoBase with its enhancements in functionality and content is publicly accessible at https://acetobase.molbio.slu.se.

bioinformatics↗

bioRxiv2021

PAOX1 expression in mixed-substrate continuous cultures of Komagataella phaffii (Pichia pastoris) is completely determined by methanol uptake regardless of the secondary carbon source: a simplifying principle for predicting recombinant protein production.

The expression of recombinant proteins by the AOX1 promoter of Komagataella phaffii is typically induced by adding methanol to the cultivation medium. Since growth on methanol imposes a high oxygen demand, the medium is often supplemented with an additional secondary carbon source which serves to reduce the consumption of methanol, and hence, oxygen. Early research recommended the use of glycerol as the secondary carbon source, but more recent studies recommend the use of sorbitol because glycerol represses PAOX1 expression. To assess the validity of this recommendation, we measured the steady state concentrations of biomass, residual methanol, and LacZ expressed from PAOX1 over a wide range of dilution rates (0.02-0.20 h-1) in continuous cultures of the Mut+ strain fed with methanol + glycerol (repressing) and methanol + sorbitol (non-repressing). We find that under these conditions, the specific PAOX1 expression rate is completely determined by the specific methanol consumption rate regardless of the type (repressing/non-repressing) of the secondary carbon source. In both cultures, the specific PAOX1 expression rate is proportional to the specific methanol consumption rate provided that the latter is below 0.15 g/(gdw-h); beyond this threshold consumption rate, the specific PAOX1 expression rate of both cultures saturates to the same value. Analysis of the data in the literature shows that the same phenomenon also occurs in continuous cultures of Escherichia coli fed with mixtures of lactose plus repressing/non-repressing carbon sources. The specific Plac expression rate is completely determined by the specific lactose consumption rate regardless of the type of secondary carbon source, glycerol or glucose. Key pointsO_LIPAOX1 expression rate is completely determined by the methanol consumption rate. C_LIO_LISorbitol is not necessarily superior secondary carbon source than glycerol. C_LI

bioengineering↗

bioRxiv2021

Deep phylo-taxono genomics reveals Xylella as a variant lineage of plant associated Xanthomonas with Stenotrophomonas and Pseudoxanthomonas as misclassified relatives

Genus Xanthomonas is a group of phytopathogens which is phylogenetically related to Xylella, Stenotrophomonas and Pseudoxanthomonas following diverse lifestyles. Xylella is a lethal plant pathogen with highly reduced genome, atypical GC content and is taxonomically related to these three genera. Deep phylo-taxono-genomics reveals that Xylella is a variant Xanthomonas lineage that is sandwiched between Xanthomonas species. Comparative studies suggest the role of unique pigment and exopolysaccharide gene clusters in the emergence of Xanthomonas and Xylella clades. Pan genome analysis identified set of unique genes associated with sub-lineages representing plant associated Xanthomonas clade and nosocomial origin Stenotrophomonas. Overall, our study reveals importance to reconcile classical phenotypic data and genomic findings in reconstituting taxonomic status of these four genera. Significance StatementXylella fastidiosa is a devastating pathogen of perennial dicots such as grapes, citrus, coffee, and olives. The pathogen is transmitted by an insect vector to its specific host wherein the infection leads to complete wilting of the plants. The genome of X. fastidiosa is extremely reduced both in terms of size (2Mb) and GC content (50%) when compared with its relatives such as Xanthomonas, Stenotrophomonas, and Pseudoxanthomonas that have higher GC content (65%) and larger genomes (5Mb). In this study, using systematic and in-depth genome-based taxonomic and phylogenetic criteria along with comparative studies, we assert the need of unification of Xanthomonas with its misclassified relatives (Xylella, Stenotrophomonas and Pseudoxanthomonas). Interestingly, Xylella revealed itself as a minor lineage embedded within two major Xanthomonas lineages comprising member species of different hosts.

genomics↗

bioRxiv2021

Exact distribution of threshold-crossing times for protein concentrations: Implication for biological timekeeping

Stochastic transcription and translation dynamics of protein accumulation up to some concentration threshold sets the timing of many cellular physiological processes. Here we obtain the exact distribution of first threshold-crossing times of protein concentration, in either Laplace or time domain, and its associated cumulants: mean, variance and skewness. The distribution is asymmetric and its skewness non-monotonically varies with the threshold. We study lysis times of E-coli cells for holin gene mutants of bacteriophage-{lambda} and find a good match with theory. Mutants requiring higher holin thresholds show more skewed lysis time distributions as predicted.

biophysics↗

bioRxiv2021

THE TRANSCRIPTIONAL RESPONSE TO OXIDATIVE STRESS IS INDEPENDENT OF STRESS-GRANULE FORMATION

Cells respond to stress with translational arrest, robust transcriptional changes, and transcription-independent formation of mRNP assemblies termed stress granules (SGs). Despite considerable interest in the role of SGs in oxidative, unfolded-protein, and viral stress responses, whether and how SGs contribute to stress-induced transcription has not been rigorously examined. To address this issue, we characterized transcriptional changes in Drosophila S2 cells induced by acute oxidative-stress and assessed how these were altered under conditions that disrupted SG assembly. Sodium-arsenite stress for 3 hours predominantly resulted in the induction or upregulation of stress-responsive mRNAs whose levels peaked during cell recovery after stress cessation. The stress-transcriptome is enriched in mRNAs coding for protein chaperones, including HSP70 and low molecular-weight heat shock proteins, glutathione transferases, and several non-coding RNAs. Oxidative stress also induced prominent cytoplasmic stress granules that disassembled 3-hours after stress cessation. As expected, RNAi-mediated knockdown of the conserved G3BP1/ Rasputin protein inhibited stress-granule assembly. However, this disruption had no significant effect on the stress-induced transcriptional response or stress-induced translational arrest. Thus, SG assembly and stress-induced effects on gene expression appear to be driven by distinctive signaling processes. We suggest that while SG assembly represents a fast, transient mechanism, the transcriptional response enables a slower, longer-lasting mechanism for adaptation to and recovery from cell stress.

cell biology↗