EGO-1, a putative RNA-dependent RNA polymerase, is required for heterochromatin assembly on unpaired dna during C. elegans meiosis.
During meiosis in C. elegans, unpaired chromosomes and chromosomal regions accumulate high levels of histone H3 lysine 9 dimethylation (H3K9me2), a modification associated with facultative heterochromatin assembly and the resulting transcriptional silencing. Meiotic silencing of unpaired DNA may be a widely conserved genome defense mechanism. The mechanisms of meiotic silencing remain unclear, although both transcriptional and posttranscriptional processes are implicated. Cellular RNA-dependent RNA polymerases (RdRPs) function in development and RNA-mediated silencing in many species and in heterochromatin assembly in S. pombe. There are four C. elegans RdRPs, including two with known germline functions. EGO-1 is required for fertility and robust germline RNAi. RRF-3 acts genetically to repress RNAi and is required for normal meiosis and spermatogenesis at elevated temperatures (S. L'Hernault, personal communication). Among C. elegans RdRPs, we find that only EGO-1 is required for H3K9me2 enrichment on unpaired chromosomal regions during meiosis. This H3K9me2 enrichment does not require Dicer or Drosha nuclease or any of several other proteins required for RNAi. ego-1 interacts genetically with him-17, another regulator of chromatin and meiosis, to promote germline development. We conclude that EGO-1 is an essential component of meiotic silencing in C. elegans.
Maine
Eleanor M
EM
Department of Biology, Syracuse University, Syracuse, New York 13244, USA. emmaine@syr.edu
Hauth
Jessica
J
Ratliff
Thomas
T
Vought
Valarie E
VE
She
Xingyu
X
Kelly
William G
WG
D000818:Animals; D017173:Caenorhabditis elegans / Q000201:enzymology* / Q000235:genetics; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D020868:Gene Silencing / Q000502:physiology*; D006570:Heterochromatin / Q000201:enzymology / Q000502:physiology*; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000378:metabolism; D008540:Meiosis / Q000235:genetics / Q000502:physiology*; D008745:Methylation; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D011496:Protein Methyltransferases; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; C491265:HIM-17 protein, C elegans; D006570:Heterochromatin; D004247:DNA; D000076983:Histone Methyltransferases; D011496:Protein Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; C406772:EGO-1 protein, C elegans; D012324:RNA-Dependent RNA Polymerase