title: EGO-1, a putative RNA-dependent RNA polymerase, is required for heterochromatin assembly on unpaired dna during C. elegans meiosis.
abstract: 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.
authors.affiliation: Department of Biology, Syracuse University, Syracuse, New York 13244, USA. emmaine@syr.edu
authors.forename: Eleanor M
authors.initials: EM
authors.lastname: Maine
authors.forename: Jessica
authors.initials: J
authors.lastname: Hauth
authors.forename: Thomas
authors.initials: T
authors.lastname: Ratliff
authors.forename: Valarie E
authors.initials: VE
authors.lastname: Vought
authors.forename: Xingyu
authors.initials: X
authors.lastname: She
authors.forename: William G
authors.initials: WG
authors.lastname: Kelly
mesh_terms: 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
chemical_list: 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