EGO-1, a putative RNA-dependent RNA polymerase, is required for heterochromatin assembly on unpaired DNA during C. elegans meiosis

• Type of Material: Article
• Authors: Eleanor M. Maine, Syracuse University; Jessica Hauth, Emory University; Thomas Ratliff, Emory University; Valarie E. Vought, Syracuse University; Xingyu She, Syracuse University; William Kelly, Emory University
• Language: English
• Date: 2005-11-08
• Publisher: Elsevier (Cell Press): 12 month embargo
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: ©2005 Elsevier Ltd All rights reserved.
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1016/j.cub.2005.09.049
• Title of Journal or Parent Work: Current Biology
• ISSN: 0960-9822
• Volume: 15
• Issue: 21
• Start Page: 1972
• End Page: 1978
• Grant/Funding Information: Some strains used in this study were provided by the Caenorhabditis Genetics Center, which is funded by the National Institutes of Health National Center for Research Resources.; Funds for this study were provided by the National Science Foundation and Syracuse University (to E.M.M.) and the National Institutes of Health and Emory University Research Council (to W.G.K.).
• Keywords: Methylation; Meiosis; RNA Replicase; Animals; Protein Methyltransferases; Caenorhabditis elegans Proteins; Histone-Lysine N-Methyltransferase; Mutation; DNA; Heterochromatin; Fluorescent Antibody Technique, Indirect; Gene Silencing; Models, Molecular; Cell Cycle Proteins; Histone Methyltransferases; Caenorhabditis elegans
• Research Categories: Biology, Cell

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 [1, 2]. Meiotic silencing of unpaired DNA may be a widely conserved genome defense mechanism [3-5]. The mechanisms of meiotic silencing remain unclear, although both transcriptional and posttranscriptional processes are implicated [3-5]. Cellular RNA-dependent RNA polymerases (RdRPs) function in development and RNA-mediated silencing in many species [3, 6, 7] and in heterochromatin assembly in S. pombe [3, 8]. There are four C. elegans RdRPs, including two with known germline functions. EGO-1 is required for fertility and robust germline RNAi [9-11]. RRF-3 acts genetically to repress RNAi and is required for normal meiosis and spermatogenesis at elevated temperatures [12] (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 [13], to promote germline development. We conclude that EGO-1 is an essential component of meiotic silencing in C. elegans.