Abstract
RNA interference is required for post-transcriptional silencing, but also has additional roles in transcriptional silencing of centromeres and genome stability. However, these roles have been controversial in mammals. Strikingly, we found that Dicer-deficient embryonic stem cells have strong proliferation and chromosome segregation defects as well as increased transcription of centromeric satellite repeats, which triggers the interferon response. We conducted a CRISPR-Cas9 genetic screen to restore viability and identified transcriptional activators, histone H3K9 methyltransferases, and chromosome segregation factors as suppressors, resembling Dicer suppressors identified in independent screens in fission yeast. The strongest suppressors were mutations in the transcriptional co-activator Brd4, which reversed the strand-specific transcription of major satellite repeats suppressing the interferon response, and in the histone acetyltransferase Elp3. We show that identical mutations in the second bromodomain of Brd4 rescue Dicer-dependent silencing and chromosome segregation defects in both mammalian cells and fission yeast. This remarkable conservation demonstrates that RNA interference has an ancient role in transcriptional silencing and in particular of satellite repeats, which is essential for cell cycle progression and proper chromosome segregation. Our results have pharmacological implications for cancer and autoimmune diseases characterized by unregulated transcription of satellite repeats.
Highlights
RNA interference is required for post-transcriptional silencing, and has additional roles in transcriptional silencing of centromeres and genome stability
While it is possible that the increase in H3K9me[3] at the pericentromeres was guided by priRNA42, we conclude that loss of small RNA and H3K9me[3] could not account for the strong phenotypes observed in Dicer1−/− mouse embryonic stem cells (mESCs)
In ES cells, our data suggest that the viability defect of Dicer1−/− cells is a consequence of transcription of the centromeric satellite repeats, and we have shown that this defect can be rescued by hypomorphic mutations in transcription factors Brd[4] and Elp[3] or by inhibiting Pol II
Summary
RNA interference is required for post-transcriptional silencing, and has additional roles in transcriptional silencing of centromeres and genome stability. We found that Dicer-deficient embryonic stem cells have strong proliferation and chromosome segregation defects as well as increased transcription of centromeric satellite repeats, which triggers the interferon response. We show that identical mutations in the second bromodomain of Brd[4] rescue Dicer-dependent silencing and chromosome segregation defects in both mammalian cells and fission yeast This remarkable conservation demonstrates that RNA interference has an ancient role in transcriptional silencing and in particular of satellite repeats, which is essential for cell cycle progression and proper chromosome segregation. Mammals lack RdRP, and we did not detect DICER1-dependent small RNAs from the major satellite transcripts in wild-type mESC (Fig. S3C), we did detect degradation products in Dicer1−/− cells resembling primary RNAs (priRNAs) observed in S. pombe[42]. We turned to a more unbiased strategy to determine the underlying mechanism
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
