1. U1 snRNP increases RNA Pol II elongation rate to enable synthesis of long genes.
- Author
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Mimoso, Claudia A. and Adelman, Karen
- Subjects
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RNA polymerase II , *RNA polymerases , *RNA , *MESSENGER RNA , *INTRONS , *GENES - Abstract
The expansion of introns within mammalian genomes poses a challenge for the production of full-length messenger RNAs (mRNAs), with increasing evidence that these long AT-rich sequences present obstacles to transcription. Here, we investigate RNA polymerase II (RNAPII) elongation at high resolution in mammalian cells and demonstrate that RNAPII transcribes faster across introns. Moreover, we find that this acceleration requires the association of U1 snRNP (U1) with the elongation complex at 5′ splice sites. The role of U1 to stimulate elongation rate through introns reduces the frequency of both premature termination and transcriptional arrest, thereby dramatically increasing RNA production. We further show that changes in RNAPII elongation rate due to AT content and U1 binding explain previous reports of pausing or termination at splice junctions and the edge of CpG islands. We propose that U1-mediated acceleration of elongation has evolved to mitigate the risks that long AT-rich introns pose to transcript completion. [Display omitted] • AT content of the transcribed region strongly impacts RNAPII elongation rate • U1 snRNP enhances transcription initiation or elongation in a gene-dependent manner • RNAPII acceleration in AT-rich sequences requires U1 snRNP • Without U1 snRNP to stimulate elongation, RNAPII is prone to arrest and termination How does RNAPII transcribe long mammalian genes, avoiding premature termination or arrest within expansive introns? Mimoso and Adelman demonstrate that splicing factor U1 snRNP increases RNAPII elongation rate within AT-rich introns, thereby reducing the likelihood of RNAPII termination or arrest. U1 snRNP is thus critical for synthesis of long genes. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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