title: Small ubiquitin-like modifier (SUMO)-mediated repression of the Xenopus Oocyte 5 S rRNA genes.
abstract: The 5 S rRNA gene-specific transcription factor IIIA (TFIIIA) interacts with the small ubiquitin-like modifier (SUMO) E3 ligase PIAS2b and with one of its targets, the transcriptional corepressor, XCtBP. PIAS2b is restricted to the cytoplasm of Xenopus oocytes but relocates to the nucleus immediately after fertilization. Following the midblastula transition, PIAS2b and XCtBP are present on oocyte-type, but not somatic-type, 5 S rRNA genes up through the neurula stage, as is a limiting amount of TFIIIA. Histone H3 methylation, coincident with the binding of XCtBP, also occurs exclusively on the oocyte-type genes. Immunohistochemical staining of embryos confirms the occupancy of a subset of the oocyte-type genes by TFIIIA that become positioned at the nuclear periphery shortly after the midblastula transition. Inhibition of SUMOylation activity relieves repression of oocyte-type 5 S rRNA genes and is correlated with a decrease in methylation of H3K9 and H3K27 and disruption of subnuclear localization. These results reveal a novel function for TFIIIA as a negative regulator that recruits histone modification activity through the CtBP repressor complex exclusively to the oocyte-type 5 S rRNA genes, leading to their terminal repression.
authors.affiliation: From the Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556.
authors.forename: Mariam Q
authors.initials: MQ
authors.lastname: Malik
authors.affiliation: From the Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Bertke
authors.affiliation: From the Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 huber.1@nd.edu.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Huber
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006657:Histones / Q000378:metabolism; D007150:Immunohistochemistry; D008239:Lysine / Q000378:metabolism; D008745:Methylation; D018613:Microscopy, Confocal; D009865:Oocytes / Q000166:cytology / Q000378:metabolism*; D011485:Protein Binding; D012341:RNA, Ribosomal, 5S / Q000235:genetics*; D058207:Sumoylation; D035582:Transcription Factor TFIIIA / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics*
chemical_list: D006657:Histones; D012341:RNA, Ribosomal, 5S; D035582:Transcription Factor TFIIIA; D029867:Xenopus Proteins; D008239:Lysine
keywords: 5 S rRNA Genes; Histone Methylation; PIAS2b; RNA Polymerase III; SUMOylation; TFIIIA; Transcription Repressor; XCtBP; Xenopus