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Ageing-associated changes in transcription and splicing efficiency influence longevity

ABSTRACT: Ageing alters cellular homeostasis thereby compromising multiple cellular processes such as transcription and splicing. However, both the extent of these changes and the molecular mechanisms are not well understood so far. In order to address this question, we analyzed transcription-coupled processes on a genomic scale in five animal species (C. elegans, D. melanogaster, M. musculus, R. norvegicus, H. sapiens) at different adult life stages. Using total RNA profiling, we quantified alterations of transcriptional elongation speed, splicing efficiency, and splicing precision. We consistently observed across all analyzed species, that the genome-average speed of RNA polymerase II (Pol-II) increased with age. These effects were reverted under lifespan-extending conditions, such as dietary restriction or modulation of insulin signaling. Reducing the speed of Pol-II in worms and flies improved splicing efficiency and increased lifespan. We further observed reduced precision in nucleosome positioning in senescent compared to proliferating cells, which correlated with reduced splicing efficiency. Thus, an age-associated increase of transcriptional speed results in reduced splicing efficiency and splicing quality. These findings substantially extend our understanding about the molecular mechanisms driving animal aging, and suggest new mechanisms underlying lifespan-extending interventions.

ORGANISM(S): Mus musculus Homo sapiens Caenorhabditis elegans Drosophila melanogaster

PROVIDER: GSE102537 | GEO | 2023/01/26

REPOSITORIES: GEO

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Regulation of RNA polymerase II processivity by Spt5 is restricted to a narrow window in elongation

Project description:Spt5 is a highly conserved RNA polymerase II (Pol II)-associated pausing and elongation factor. However, its impact on global elongation and Pol II processivity in mammalian cells has not been clarified. Here, we show that depleting Spt5 in mouse embryonic fibroblasts (MEFs) does not cause global elongation defects or decreased elongation rates. Instead, in the absence of Spt5, a fraction of Pol II molecules are dislodged during elongation thus decreasing the number of Pol II complexes that complete the transcription cycle. Most strikingly, this decrease is restricted to a narrow window between 15-20 kb from the promoter, a distance which coincides with the stage where accelerating Pol II attains maximum elongation speed and processivity. Consequently, long genes show a greater dependency on Spt5 for optimal elongation efficiency and overall gene expression than short genes. We propose that an important role of Spt5 in mammalian elongation is to promote the processivity of those Pol II complexes that are transitioning towards maximum elongation speed 15-20 kb from the promoter.

2018-03-06 | GSE106313 | GEO

Alternative RNA Stuctures Formed During Transcription Depend on Elongation Rate and Modify RNA processing

Project description:Most RNA processing occurs co-transcriptionally. We interrogated nascent pol II transcripts by chemical and enzymatic probing, and determined how the “nascent RNA structureome” relates to splicing, A-I editing and transcription speed. RNA folding within introns and steep structural transitions at splice sites are associated with efficient co-transcriptional splicing. A slow pol II mutant elicits extensive remodeling into more folded conformations with increased A-I editing. Introns that become more structured at their 3’ splice sites get co-transcriptionally excised more efficiently. Slow pol II altered folding of intronic Alu elements where cryptic splicing and intron retention are stimulated, an outcome mimicked by UV which decelerates transcription. Slow transcription also remodeled RNA folding around alternative exons in distinct ways that predict whether skipping or inclusion is favored, even though it occurs post-transcriptionally. Hence co-transcriptional RNA folding modulates post-transcriptional alternative splicing. In summary the plasticity of nascent transcripts has widespread effects on RNA processing.

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2022-08-09 | PXD035866 | iProX

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2022-06-15 | GSE186273 | GEO

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Project description:Transcription regulation occurs frequently through promoter-associated pausing of RNA polymerase II (Pol II). We developed a Precision nuclear Run-On and sequencing assay (PRO-seq) to map the genome-wide distribution of transcriptionally-engaged Pol II at base-pair resolution. Pol II accumulates immediately downstream of promoters, at intron-exon junctions that are efficiently used for splicing, and over 3' poly-adenylation sites. Focused analyses of promoters reveal that pausing is not fixed relative to initiation sites nor is it specified directly by the position of a particular core promoter element or the first nucleosome. Core promoter elements function beyond initiation, and when optimally positioned they act collectively to dictate the position and strength of pausing . We test this ‘Complex Interaction’ model with insertional mutagenesis of the Drosophila Hsp70 core promoter.

2013-02-01 | GSE42117 | GEO

Precise Maps of RNA Polymerase Reveal How Promoters Direct Initiation and Pausing

2013-02-01 | E-GEOD-42117 | biostudies-arrayexpress

Global impact of RNA polymerase II elongation inhibition on alternative splicing regulation (expression)

Project description:The rate of RNA polymerase II (pol II) elongation can influence splice site selection in nascent transcripts, yet the extent and physiological relevance of this kinetic coupling between transcription and alternative splicing is not well understood. We performed experiments to perturb pol II elongation and then globally compared alternative splicing patterns with genome-wide pol II occupancy. RNA binding and RNA processing functions were significantly enriched among the genes with pol II elongation inhibition-dependent changes in alternative splicing. Under conditions that interfere with pol II elongation, including cell stress, increased pol II occupancy was detected in the intronic regions flanking the alternative exons in these genes, and these exons generally became more included. A disproportionately high fraction of these exons introduced premature termination codons that elicited nonsense-mediated mRNA decay (NMD), thereby further reducing transcript levels. Our results provide evidence that kinetic coupling between transcription, alternative splicing and NMD affords a rapid mechanism by which cells can respond to changes in growth conditions, including cell stress, to coordinate the levels of RNA processing factors with mRNA levels. In order to identify alternative splicing events influenced by changes in pol II elongation, we performed quantitative alternative splicing microarray profiling (Pan et al., 2004 (PMID 15610736); Shai et al., 2006 (PMID 16403798)) of RNA isolated from stimulated Jurkat T lymphoma cells, cultured separately in the presence or absence of two different drugs that can inhibit pol II elongation: 5,6-dichloro-1-β-D-ribofuranosyl-benzimidazole (DRB) and camptothecin.

2010-12-09 | E-GEOD-25287 | biostudies-arrayexpress

Global impact of RNA polymerase II elongation inhibition on alternative splicing regulation (ChIP-Seq)

Project description:The rate of RNA polymerase II (pol II) elongation can influence splice site selection in nascent transcripts, yet the extent and physiological relevance of this kinetic coupling between transcription and alternative splicing is not well understood. We performed experiments to perturb pol II elongation and then globally compared alternative splicing patterns with genome-wide pol II occupancy. RNA binding and RNA processing functions were significantly enriched among the genes with pol II elongation inhibition-dependent changes in alternative splicing. Under conditions that interfere with pol II elongation, including cell stress, increased pol II occupancy was detected in the intronic regions flanking the alternative exons in these genes, and these exons generally became more included. A disproportionately high fraction of these exons introduced premature termination codons that elicited nonsense-mediated mRNA decay (NMD), thereby further reducing transcript levels. Our results provide evidence that kinetic coupling between transcription, alternative splicing and NMD affords a rapid mechanism by which cells can respond to changes in growth conditions, including cell stress, to coordinate the levels of RNA processing factors with mRNA levels. To monitor pol II distributions, chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-Seq) was performed using an anti-pol II antibody (4H8) and cross-linked chromatin preparations from Jurkat cells, treated with or without pol II elongation inhibitor 5,6-dichloro-1-β-D-ribofuranosyl-benzimidazole (DRB) at 10 and 25 ug/ml respectively prior to phorbol 12-myristate 13-acetate (PMA) stimulation, for 5000+ alternative splicing events.

2010-12-09 | E-GEOD-25494 | biostudies-arrayexpress

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