Transcription-Austin最新文献

RNA processing encompasses the capping, cleavage, polyadenylation and alternative splicing of pre-mRNA. Proper muscle development relies on precise RNA processing, driven by the coordination between RNA-binding proteins. Recently, skeletal muscle biology has been intensely investigated in terms of RNA processing. High throughput studies paired with deletion of RNA-binding proteins have provided a high-level understanding of the molecular mechanisms controlling the regulation of RNA-processing in skeletal muscle. Furthermore, misregulation of RNA processing is implicated in muscle diseases. In this review, we comprehensively summarize recent studies in skeletal muscle that demonstrated: (i) the importance of RNA processing, (ii) the RNA-binding proteins that are involved, and (iii) diseases associated with defects in RNA processing.

SAGA and NuA4 are coactivator complexes required for transcription on chromatin. Although they contain different enzymatic and biochemical activities, both contain the large Tra1 subunit. Recent electron microscopy studies have resolved the complete structure of Tra1 and its integration in SAGA/NuA4, providing important insight into Tra1 function.

SAGA and TFIID are related transcription complexes, which were proposed to alternatively deliver TBP at different promoter classes. Recent genome-wide studies in yeast revealed that both complexes are required for the transcription of a vast majority of genes by RNA polymerase II raising new questions about the role of coactivators.

In yeast, transcription of ribosomal DNA (rDNA) by RNA polymerase I (Pol I) is regulated by unique mechanisms acting at the level of the enzyme. Under stress situations such as starvation, Pol I hibernates through dimerization. When growth conditions are restored, dimer disassembly and Rrn3 binding drive enzyme activation and subsequent recruitment to rDNA.

Transcription by RNA polymerase II (Pol II) is accomplished with the aid of numerous accessory factors specific to each transcriptional stage. The structure of the Pol II elongation complex (EC) bound with Spt4/5, Elf1, and TFIIS unveiled the sophisticated basal EC architecture essential for transcription elongation and other transcription-related events.

Based on molecular dynamics simulations and functional studies, a conformational mechanism is posited for forward translocation by RNA polymerase (RNAP). In a simulation of a ternary elongation complex, the clamp and downstream cleft were observed to close. Hinges within the bridge helix and trigger loop supported generation of translocation force against the RNA-DNA hybrid resulting in opening of the furthest upstream i-8 RNA-DNA bp, establishing conditions for RNAP sliding. The β flap tip helix and the most N-terminal β' Zn finger engage the RNA, indicating a path of RNA threading out of the exit channel. Because the β flap tip connects to the RNAP active site through the β subunit double-Ψ-β-barrel and the associated sandwich barrel hybrid motif (also called the flap domain), the RNAP active site is coupled to the RNA exit channel and to the translocation of RNA-DNA. Using an exonuclease III assay to monitor translocation of RNAP elongation complexes, we show that K⁺ and Mg²⁺ and also an RNA 3'-OH or a 3'-H₂ affect RNAP sliding. Because RNAP grip to template suggests a sticky translocation mechanism, and because grip is enhanced by increasing K⁺ and Mg²⁺concentration, biochemical assays are consistent with a conformational change that drives forward translocation as observed in simulations. Mutational analysis of the bridge helix indicates that 778-GARKGL-783 (Escherichia coli numbering) is a homeostatic hinge that undergoes multiple bends to compensate for complex conformational dynamics during phosphodiester bond formation and translocation.

Transcription of protein-encoding genes in eukaryotic cells is a dynamically coordinated process. Many of the key transcription regulators contain functionally essential intrinsically disordered regions (IDRs), the dynamic nature of which creates extra challenges to traditional biochemical analyses. Recent advances in single-molecule fluorescence imaging technology have enabled direct visualization of these rapid, complex and dynamic molecular interactions in real time.

Sma and Mad related (SMAD)-mediated Transforming Growth Factor β (TGF-β) and Bone Morphogenetic Protein (BMP) signaling is required for various cellular processes. The activated heterotrimeric SMAD protein complexes associate with nuclear proteins such as the histone acetyltransferases p300, PCAF and the Mixed Lineage Leukemia 4 (MLL4) subunit Pax Transactivation domain-Interacting Protein (PTIP) to regulate gene transcription. We investigated the functional role of PTIP and PTIP Interacting protein 1 (PA1) in relation to TGF-β-activated SMAD signaling. We immunoprecipitated PTIP and PA1 with all SMAD family members to identify the TGF-β and not BMP-specific SMADs as interacting proteins. Gene silencing experiments of MLL4 and the subunits PA1 and PTIP confirm TGF-β-specific genes to be regulated by the MLL4 complex, which links TGF-β signaling to transcription regulation by the MLL4 methyltransferase complex.

LncRNAs are novel noncoding RNAs involved in the epigenetic regulation of gene expression by recruiting ribonucleoprotein complexes to specific genomic loci to initiate histone methylation and/or other chromatin modifications. LncRNAs themselves function as tumor suppressors or oncogenes, depending on the gene regulatory networks they govern. We identified lnc00673 (ERRLR01) as a marker of overall survival (OS) in breast cancer patients. Specifically, ERRLR01 levels were elevated in triple-negative breast cancer (TNBC) as compared with Luminal-A, Luminal-B, and HER2 breast cancer subtypes. ERRLR01 levels were also inversely correlated with breast cancer survival across all breast cancer patients. Upon stratification, OS in ERα^- tumors correlated with negative overall survival, while in ERα⁺ tumors, ERRLR01 correlated with positive outcomes. This suggests ERRLR01 is modulated by hormone signaling in breast cancer. Gene-network analysis revealed ERRLR01 correlated with distinct pathways including "epithelial development" and "cellular differentiation." These data suggest ERRLR01 operates as an oncogene in TNBC, as well as a biomarker in breast cancer patients.

Helicases are enzymes that remodel nucleic acids or protein-nucleic acid complexes in an ATP-dependent manner. They are ubiquitous and can play many diverse functions related to the metabolism of nucleic acids. A few helicases from both the prokaryotic and the eukaryotic worlds have the ability to induce transcription termination. Here we discuss how the same biological function is achieved by different helicases with quite divergent structures and mechanisms of action.