title: MRG-1, an autosome-associated protein, silences X-linked genes and protects germline immortality in Caenorhabditis elegans.
abstract: MRG15, a mammalian protein related to the mortality factor MORF4, is required for cell proliferation and embryo survival. Our genetic analysis has revealed that the Caenorhabditis elegans ortholog MRG-1 serves similar roles. Maternal MRG-1 promotes embryo survival and is required for proliferation and immortality of the primordial germ cells (PGCs). As expected of a chromodomain protein, MRG-1 associates with chromatin. Unexpectedly, it is concentrated on the autosomes and not detectable on the X chromosomes. This association is not dependent on the autosome-enriched protein MES-4. Focusing on possible roles of MRG-1 in regulating gene expression, we determined that MRG-1 is required to maintain repression in the maternal germ line of transgenes on extrachromosomal arrays, and of several X-linked genes previously shown to depend on MES-4 for repression. MRG-1 is not required for PGCs to acquire transcriptional competence or for the turn-on of expression of several PGC-expressed genes (pgl-1, glh-1, glh-4 and nos-1). By contrast to this result in PGCs, MRG-1 is required for ectopic expression of those germline genes in somatic cells lacking the NuRD complex component MEP-1. We discuss how an autosome-enriched protein might repress genes on the X chromosome, promote PGC proliferation and survival, and influence the germ versus soma distinction.
authors.affiliation: Department of Biology, Graduate School of Science and Technology, Kobe University, 1-1 Rokkodaicho, Nadaku, Kobe 657-8501, Japan.
authors.forename: Teruaki
authors.initials: T
authors.lastname: Takasaki
authors.forename: Zheng
authors.initials: Z
authors.lastname: Liu
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Habara
authors.forename: Kiyoji
authors.initials: K
authors.lastname: Nishiwaki
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Nakayama
authors.forename: Kunio
authors.initials: K
authors.lastname: Inoue
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sakamoto
authors.forename: Susan
authors.initials: S
authors.lastname: Strome
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins / Q000502:physiology*; D049109:Cell Proliferation; D002470:Cell Survival; D020868:Gene Silencing / Q000502:physiology*; D050172:Genes, X-Linked / Q000235:genetics*; D005854:Germ Cells / Q000166:cytology*; D012097:Repressor Proteins; D014960:X Chromosome
chemical_list: D029742:Caenorhabditis elegans Proteins; C470832:MRG-1 protein, C elegans; D012097:Repressor Proteins