title: Piwi Modulates Chromatin Accessibility by Regulating Multiple Factors Including Histone H1 to Repress Transposons.
abstract: PIWI-interacting RNAs (piRNAs) mediate transcriptional and post-transcriptional silencing of transposable element (TE) in animal gonads. In Drosophila ovaries, Piwi-piRNA complexes (Piwi-piRISCs) repress TE transcription by modifying the chromatin state, such as by H3K9 trimethylation. Here, we demonstrate that Piwi physically interacts with linker histone H1. Depletion of Piwi decreases H1 density at a subset of TEs, leading to their derepression. Silencing at these loci separately requires H1 and H3K9me3 and heterochromatin protein 1a (HP1a). Loss of H1 increases target loci chromatin accessibility without affecting H3K9me3 density at these loci, while loss of HP1a does not impact H1 density. Thus, Piwi-piRISCs require both H1 and HP1a to repress TEs, and the silencing is correlated with the chromatin state rather than H3K9me3 marks. These findings suggest that Piwi-piRISCs regulate the interaction of chromatin components with target loci to maintain silencing of TEs through the modulation of chromatin accessibility.
authors.affiliation: Department of Molecular Biology, Keio University School of Medicine, Tokyo 160-8582, Japan.
authors.forename: Yuka W
authors.initials: YW
authors.lastname: Iwasaki
authors.affiliation: Department of Molecular Biology, Keio University School of Medicine, Tokyo 160-8582, Japan.
authors.forename: Kensaku
authors.initials: K
authors.lastname: Murano
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0032, Japan.
authors.forename: Hirotsugu
authors.initials: H
authors.lastname: Ishizu
authors.affiliation: Department of Molecular Biology, Keio University School of Medicine, Tokyo 160-8582, Japan.
authors.forename: Aoi
authors.initials: A
authors.lastname: Shibuya
authors.affiliation: Department of Molecular Biology, Keio University School of Medicine, Tokyo 160-8582, Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Iyoda
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0032, Japan.
authors.forename: Mikiko C
authors.initials: MC
authors.lastname: Siomi
authors.affiliation: Department of Molecular Biology, Keio University School of Medicine, Tokyo 160-8582, Japan. Electronic address: awa403@keio.jp.
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Siomi
authors.affiliation: Department of Molecular Biology, Keio University School of Medicine, Tokyo 160-8582, Japan. Electronic address: saito@z6.keio.jp.
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Saito
mesh_terms: D000818:Animals; D060565:Argonaute Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D042002:Chromatin Assembly and Disassembly; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D004251:DNA Transposable Elements; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D063185:Epigenetic Repression; D005260:Female; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D010053:Ovary / Q000166:cytology / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: D060565:Argonaute Proteins; D002868:Chromosomal Proteins, Non-Histone; D004251:DNA Transposable Elements; D029721:Drosophila Proteins; D006657:Histones; D034741:RNA, Small Interfering; C116498:piwi protein, Drosophila; D000090266:Chromobox Protein Homolog 5