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Cell Rep. 2017 Jun 20;19(12):2477-2489. doi: 10.1016/j.celrep.2017.05.086.

The Conserved RNA Binding Cyclophilin, Rct1, Regulates Small RNA Biogenesis and Splicing Independent of Heterochromatin Assembly.

Author information

1
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA; Molecular and Cellular Biology Program, Stony Brook University, Stony Brook, NY 11794, USA.
2
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA; Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
3
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
4
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA; Molecular and Cellular Biology Program, Stony Brook University, Stony Brook, NY 11794, USA; Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA; Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA. Electronic address: martiens@cshl.edu.

Abstract

RNAi factors and their catalytic activities are essential for heterochromatin assembly in S. pombe. This has led to the idea that siRNAs can promote H3K9 methylation by recruiting the cryptic loci regulator complex (CLRC), also known as recombination in K complex (RIKC), to the nucleation site. The conserved RNA-binding protein Rct1 (AtCyp59/SIG-7) interacts with splicing factors and RNA polymerase II. Here we show that Rct1 promotes processing of pericentromeric transcripts into siRNAs via the RNA recognition motif. Surprisingly, loss of siRNA in rct1 mutants has no effect on H3K9 di- or tri-methylation, resembling other splicing mutants, suggesting that post-transcriptional gene silencing per se is not required to maintain heterochromatin. Splicing of the Argonaute gene is also defective in rct1 mutants and contributes to loss of silencing but not to loss of siRNA. Our results suggest that Rct1 guides transcripts to the RNAi machinery by promoting splicing of elongating non-coding transcripts.

KEYWORDS:

H3K9 methylation; RNA interference; RNAi; RRM-containing cyclophilin regulating transcription; Rct1; exosome; heterochromatin silencing; non-coding transcripts; siRNA; small interfering RNA; splicing

PMID:
28636937
PMCID:
PMC5600480
DOI:
10.1016/j.celrep.2017.05.086
[Indexed for MEDLINE]
Free PMC Article

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