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The conserved RNA-binding protein Seb1 promotes cotranscriptional ribosomal RNA processing by controlling RNA polymerase I progression

ABSTRACT: Transcription by RNA polymerase I (RNAPI) represents the majority of the transcriptional activity in eukaryotic cells and is associated with the production of mature ribosomal rRNAs (rRNAs). As several rRNA maturation steps are coupled to RNAPI transcription, the rate of RNAPI elongation directly influences processing of nascent rRNA, and changes in RNAPI transcription rate can result in alternative rRNA processing pathways in response to growth conditions and stress. However, factors and mechanisms that control RNAPI progression by influencing transcription elongation rate remain poorly understood. We show here that the conserved fission yeast RNA-binding protein Seb1 associates with the RNAPI transcription machinery and promotes RNAPI pausing states along the rDNA. The overall faster progression of RNAPI at the rDNA in Seb1-deficient cells impaired cotranscriptional rRNA processing and the production of mature rRNAs. Given that Seb1 also influences pre-mRNA processing by modulating RNAPII progression, our findings unveil Seb1 as a pausing-promoting factor for RNA polymerases I and II to control cotranscriptional RNA processing.

ORGANISM(S): Schizosaccharomyces pombe

PROVIDER: GSE212930 | GEO | 2023/05/02

REPOSITORIES: GEO

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Seb1 proximity dependent biotinylation (PDB) in Schizosaccharomyces pombe

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2023-05-02 | PXD037768 | Pride

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Project description:Ribosomal RNAs (rRNAs) are essential components of the ribosome and are among the most abundant macromolecules in the cell. To ensure high rRNA level, eukaryotic genomes contain dozens to hundreds of rDNA genes, however, only a fraction of the rRNA genes seems to be active, while others are transcriptionally silent. In Drosophila rDNA units damaged by insertions of retrotransposons are repressed by an unknown mechanism. Here, we established a new model to study regulation of rDNA expression using molecularly marked rDNA transgenes. Using this model, we show that insertion of any heterologous sequence into rDNA leads to transcriptional repression. We found that SUMO (Small Ubiquitin-like Modifier) is required for efficient repression of damaged rDNA units. Surprisingly, SUMO also controls expression of intact rDNA, demonstrating that a single pathway is responsible for both selective repression of damaged units and silencing of surplus rDNA.

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Erroneous ribosomal RNAs promote the generation of antisense ribosomal siRNA

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The Nrd1-like protein Seb1 coordinates co-transcriptional 3â end processing and polyadenylation site selection

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