Transcription-Austin最新文献

Transcription regulation is an important mechanism that controls pluripotency and differentiation. Transcription factors dictate cell fate decisions by functioning cooperatively with chromatin regulators. We have recently demonstrated that BEND3 (BANP, E5R and Nac1 domain) protein regulates the expression of differentiation-associated genes by modulating the chromatin architecture at promoters. We highlight the collaboration of BEND3 with the polycomb repressive complex in coordinating transcription repression and propose a model highlighting the relevance of the BEND3-PRC2 axis in gene regulation and chromatin organization.Abbreviations: BEND3, BANP, E5R and Nac1 domain; rDNA, ribosomal DNA; PRC2, Polycomb Repressive Complex 2; H3K27me3, Histone H3 Lysine 27 methylation; PcG, Polycomb group.

The identification of FACT as a histone chaperone enabling transcription through chromatin in vitro has strongly shaped how its roles are envisioned. However, FACT has been implicated in essentially all aspects of chromatin biology, from transcription to DNA replication, DNA repair, and chromosome segregation. In this review, we focus on recent literature describing the role and mechanisms of FACT during transcription. We highlight the prime importance of FACT in preserving chromatin integrity during transcription and challenge its role as an elongation factor. We also review evidence for FACT's role as a cell-type/gene-specific regulator of gene expression and briefly summarize current efforts at using FACT inhibition as an anti-cancer strategy.

N-terminal methylation (Nα-methylation) by the methyltransferase NRMT1 is an important post-translational modification that regulates protein-DNA interactions. Accordingly, its loss impairs functions that are reliant on such interactions, including DNA repair and transcriptional regulation. The global loss of Nα-methylation results in severe developmental and premature aging phenotypes, but given over 300 predicted substrates, it is hard to discern which physiological substrates contribute to each phenotype. One of the most striking phenotypes in NRMT1 knockout (Nrmt1^-/-) mice is early liver degeneration. To identify the disrupted signaling pathways leading to this phenotype and the NRMT1 substrates involved, we performed RNA-sequencing analysis of control and Nrmt1^-/- adult mouse livers. We found both a significant upregulation of transcripts in the cytochrome P450 (CYP) family and downregulation of transcripts in the major urinary protein (MUP) family. Interestingly, transcription of both families is inversely regulated by the transcription factor zinc fingers and homeoboxes 2 (ZHX2). ZHX2 contains a non-canonical NRMT1 consensus sequence, indicating that its function could be directly regulated by Nα-methylation. We confirmed misregulation of CYP and MUP mRNA and protein levels in Nrmt1^-/- livers and verified NRMT1 can methylate ZHX2 in vitro. In addition, we used a mutant of ZHX2 that cannot be methylated to directly demonstrate Nα-methylation promotes ZHX2 transcription factor activity and target promoter occupancy. Finally, we show Nrmt1^-/- mice also exhibit early postnatal de-repression of ZHX2 targets involved in fetal liver development. Taken together, these data implicate ZHX2 misregulation as a driving force behind the liver phenotype seen in Nrmt1^-/- mice.

Transcription elongation by RNA polymerase II (Pol II) has emerged as a regulatory hub in gene expression. A key control point occurs during early transcription elongation when Pol II pauses in the promoter-proximal region at the majority of genes in mammalian cells and at a large set of genes in Drosophila. An increasing number of trans-acting factors have been linked to promoter-proximal pausing. Some factors help to establish the pause, whereas others are required for the release of Pol II into productive elongation. A dysfunction of this elongation control point leads to aberrant gene expression and can contribute to disease development. The BET bromodomain protein BRD4 has been implicated in elongation control. However, only recently direct BRD4-specific functions in Pol II transcription elongation have been uncovered. This mainly became possible with technological advances that allow selective and rapid ablation of BRD4 in cells along with the availability of approaches that capture the immediate consequences on nascent transcription. This review sheds light on the experimental breakthroughs that led to the emerging view of BRD4 as a general regulator of transcription elongation.

Initially discovered by genetic screens in budding yeast, SPT5 and its partner SPT4 form a stable complex known as DSIF in metazoa, which plays pleiotropic roles in multiple steps of transcription. SPT5 is the most conserved transcription elongation factor, being found in all three domains of life; however, its structure has evolved to include new domains and associated posttranslational modifications. These gained features have expanded transcriptional functions of SPT5, likely to meet the demand for increasingly complex regulation of transcription in higher organisms. This review discusses the pleiotropic roles of SPT5 in transcription, including RNA polymerase II (Pol II) stabilization, enhancer activation, Pol II pausing and its release, elongation, and termination, with a focus on the most recent progress of SPT5 functions in regulating metazoan transcription.

The C-terminal domain (CTD) of the largest subunit of RNA polymerase II (Pol II) consists of YSPTSPS heptapeptide repeats, and the phosphorylation status of the repeats controls multiple transcriptional steps and co-transcriptional events. However, how CTD phosphorylation status responds to distinct environmental stresses is not fully understood. In this study, we found that a drastic reduction in phosphorylation of a subset of Ser2 residues occurs rapidly but transiently following exposure to H₂O₂. ChIP analysis indicated that Ser2-P, and to a lesser extent Tyr1-P was reduced only at the gene 3' end. Significantly, the levels of polyadenylation factor CstF77, as well as Pol II, were also reduced. However, no increase in uncleaved or readthrough RNA products was observed, suggesting transcribing Pol II prematurely terminates at the gene end in response to H₂O₂. Further analysis found that the reduction of Ser2-P is, at least in part, regulated by CK2 but independent of FCP1 and other known Ser2 phosphatases. Finally, the H₂O₂ treatment also affected snRNA 3' processing although surprisingly the U2 processing was not impaired. Together, our data suggest that H₂O₂ exposure creates a unique CTD phosphorylation state that rapidly alters transcription to deal with acute oxidative stress, perhaps creating a novel "emergency brake" mechanism to transiently dampen gene expression.

RNA modifications are prevalent among all the classes of RNA, regulate diverse biological processes, and have emerged as a key regulatory mechanism in post-transcriptional control of gene expression. They are subjected to precise spatial and temporal control and shown to be critical for the maintenance of normal development and physiology. For example, m⁶A modification of mRNA affects stability, recruitment of RNA binding protein (RBP), translation, and splicing. The deposition of m6A on the RNA happens co-transcriptionally, allowing the tight coupling between the transcription and RNA modification machinery. The m⁶A modification is affected by transcriptional dynamics, but recent insights also suggest that m⁶A machinery impacts transcription and chromatin signature.

The Integrator was originally discovered as a specialized 3'-end processing endonuclease complex required for maturation of RNA polymerase II (RNAPII)-dependent small nuclear RNAs (snRNAs). Since its discovery, Integrator's spectrum of substrates was significantly expanded to include non-polyadenylated long noncoding RNAs (lncRNA), enhancer RNAs (eRNAs), telomerase RNA (tertRNA), several Herpesvirus transcripts, and messenger RNAs (mRNAs). Recently emerging transcriptome-wide studies reveled an important role of the Integrator in protein-coding genes, where it contributes to gene expression regulation through promoter-proximal transcription attenuation. These new functional data are complemented by several structures of Integrator modules and higher-order complexes, providing mechanistic insights into Integrator-mediated processing events. In this work, we summarize recent progress in our understanding of the structure and function of the Integrator complex.

Coordination between the molecular machineries that synthesize and decode prokaryotic mRNAs is an important layer of gene expression control known as transcription-translation coupling. While it has long been known that translation can regulate transcription and vice-versa, recent structural and biochemical work has shed light on the underlying mechanistic basis. Complexes of RNA polymerase linked to a trailing ribosome (expressomes) have been structurally characterized in a variety of states at near-atomic resolution, and also directly visualized in cells. These data are complemented by recent biochemical and biophysical analyses of transcription-translation systems and the individual components within them. Here, we review our improved understanding of the molecular basis of transcription-translation coupling. These insights are discussed in relation to our evolving understanding of the role of coupling in cells.

The low G + C Gram-positive bacteria represent some of the most medically and industrially important microorganisms. They are relied on for the production of food and dietary supplements, enzymes and antibiotics, as well as being responsible for the majority of nosocomial infections and serving as a reservoir for antibiotic resistance. Control of gene expression in this group is more highly studied than in any bacteria other than the Gram-negative model  Escherichia coli, yet until recently no structural information on RNA polymerase (RNAP) from this group was available. This review will summarize recent reports on the high-resolution structure of RNAP from the model low G + C representative  Bacillus subtilis, including the role of auxiliary subunits δ and ε, and outline approaches for the development of antimicrobials to target RNAP from this group.