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sexta-feira, outubro 17, 2014

Dicer Promotes Transcription Termination at Sites of Replication Stress to Maintain Genome Stability

Stephane E. Castel4, Jie Ren4, Sonali Bhattacharjee, An-Yun Chang, Mar Sánchez, Alberto Valbuena, Francisco Antequera, Robert A. Martienssen email 4 Co-first author



•Dcr1 has a genome-wide role in terminating Pol II transcription

•Dcr1 termination occurs at highly transcribed protein coding genes, tDNA, and rDNA

•Targets are sites of transcription-replication collisions with DNA damage

•Dcr1 resolves collisions, preventing restart by HR, maintaining genomic stability


Nuclear RNAi is an important regulator of transcription and epigenetic modification, but the underlying mechanisms remain elusive. Using a genome-wide approach in the fission yeast S. pombe, we have found that Dcr1, but not other components of the canonical RNAi pathway, promotes the release of Pol II from the 3′ end of highly transcribed genes, and, surprisingly, from antisense transcription of rRNA and tRNA genes, which are normally transcribed by Pol I and Pol III. These Dcr1-terminated loci correspond to sites of replication stress and DNA damage, likely resulting from transcription-replication collisions. At the rDNA loci, release of Pol II facilitates DNA replication and prevents homologous recombination, which would otherwise lead to loss of rDNA repeats especially during meiosis. Our results reveal a novel role for Dcr1-mediated transcription termination in genome maintenance and may account for widespread regulation of genome stability by nuclear RNAi in higher eukaryotes.



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