Raf1 Is a DCAF for the Rik1 DDB1-like protein and has separable roles in siRNA generation and chromatin modification.
Non-coding transcription can trigger histone post-translational modifications forming specialized chromatin. In fission yeast, heterochromatin formation requires RNAi and the histone H3K9 methyltransferase complex CLRC, composed of Clr4, Raf1, Raf2, Cul4, and Rik1. CLRC mediates H3K9 methylation and siRNA production; it also displays E3-ubiquitin ligase activity in vitro. DCAFs act as substrate receptors for E3 ligases and may couple ubiquitination with histone methylation. Here, structural alignment and mutation of signature WDxR motifs in Raf1 indicate that it is a DCAF for CLRC. We demonstrate that Raf1 promotes H3K9 methylation and siRNA amplification via two distinct, separable functions. The association of the DCAF Raf1 with Cul4-Rik1 is critical for H3K9 methylation, but dispensable for processing of centromeric transcripts into siRNAs. Thus the association of a DCAF, Raf1, with its adaptor, Rik1, is required for histone methylation and to allow RNAi to signal to chromatin.
Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, United Kingdom.
Alessia
A
Buscaino
Sharon A
SA
White
Douglas R
DR
Houston
Erwan
E
Lejeune
Femke
F
Simmer
Flavia
F
de Lima Alves
Piyush T
PT
Diyora
Takeshi
T
Urano
Elizabeth H
EH
Bayne
Juri
J
Rappsilber
Robin C
RC
Allshire
D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins / Q000235:genetics; D042002:Chromatin Assembly and Disassembly; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D006570:Heterochromatin / Q000235:genetics; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics; D006657:Histones / Q000235:genetics*; D006801:Humans; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics; D046912:Multiprotein Complexes / Q000235:genetics; D009154:Mutation; D011499:Protein Processing, Post-Translational; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics*; D012568:Schizosaccharomyces / Q000235:genetics* / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics*; D040681:Structural Homology, Protein; D044767:Ubiquitin-Protein Ligases / Q000235:genetics; D054875:Ubiquitination
D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; C500125:Ddb1 protein, S pombe; D006570:Heterochromatin; D006657:Histones; D046912:Multiprotein Complexes; D034741:RNA, Small Interfering; C513898:Raf2 protein, S pombe; C489651:Rik1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; C577504:slp1 protein, S pombe; D008780:Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; C112744:clr4 protein, S pombe; D044767:Ubiquitin-Protein Ligases; D019908:Proto-Oncogene Proteins c-raf