title: Novel functional small RNAs are selectively loaded onto mammalian Ago1.
abstract: Argonaute (Ago) proteins function in RNA silencing as components of the RNA-induced silencing complex (RISC). In lower organisms, the small interfering RNA and miRNA pathways diverge due in part to sorting mechanisms that direct distinct small RNA (sRNA) duplexes onto specific Ago-RISCs. However, such sorting mechanisms appear to be lost in mammals. miRNAs appear not to distinguish among Ago1-4. To determine the effect of viral infection on the sorting system, we compared the content of deep-sequenced RNA extracted from immunoprecipitation experiments with the Ago1 and Ago2 proteins using Epstein-Barr virus (EBV)-infected cells. Consistent with previous observations, sequence tags derived from miRNA loci in EBV and humans globally associate in approximately equivalent amounts with Ago1 and Ago2. Interestingly, additional sRNAs, which have not been registered as miRNAs, were associated with Ago1. Among them, some unique sequence tags derived from tandem loci in the human genome associate exclusively with Ago1 but not, or rarely, with Ago2. This is supported by the observation that the expression of the unique sRNAs in the cells is highly dependent on Ago1 proteins. When we knocked down Ago1, the expression of the Ago1-specific sRNAs decreased dramatically. Most importantly, the Ago1-specific sRNAs bound to mRNAs and regulated target genes and were dramatically upregulated, depending on the EBV life cycle. Therefore, even in mammals, the sorting mechanism in the Ago1-4 family is functional. Moreover, the existence of Ago1-specific sRNAs implies vital roles in some aspects of mammalian biology.
authors.affiliation: Department of Regenerative Medicine, Division of Basic Clinical Science, Tokai University School of Medicine, Isehara, Kanagawa 259-1193, Japan, Department of Molecular Oncology and Leukemia Program Project, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8553, Japan, Wellcome Trust Centre for Cell Biology, The University of Edinburgh, Edinburgh, EH9 3JR, UK, Department of Infectious Diseases, National Research Institute for Child Health and Development, Tokyo 157-0074, Japan, Department of Biosciences, School of Science, Kitasato University, Kanagawa 252-0373, Japan, Research Center for Regenerative Medicine, Tokai University School of Medicine, Kanagawa 259-1193, Japan and Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan.
authors.forename: Natsuko
authors.initials: N
authors.lastname: Yamakawa
authors.forename: Kazuki
authors.initials: K
authors.lastname: Okuyama
authors.forename: Jun
authors.initials: J
authors.lastname: Ogata
authors.forename: Akinori
authors.initials: A
authors.lastname: Kanai
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Helwak
authors.forename: Masako
authors.initials: M
authors.lastname: Takamatsu
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Imadome
authors.forename: Kohei
authors.initials: K
authors.lastname: Takakura
authors.forename: Bidisha
authors.initials: B
authors.lastname: Chanda
authors.forename: Natsumi
authors.initials: N
authors.lastname: Kurosaki
authors.forename: Haruna
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Ando
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Matsui
authors.forename: Toshiya
authors.initials: T
authors.lastname: Inaba
authors.forename: Ai
authors.initials: A
authors.lastname: Kotani
mesh_terms: D060565:Argonaute Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D039642:Eukaryotic Initiation Factors / Q000378:metabolism*; D004854:Herpesvirus 4, Human / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D006801:Humans; D035683:MicroRNAs / Q000378:metabolism; D034622:RNA Interference; D058727:RNA, Small Untranslated / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D043244:Ribonuclease III / Q000378:metabolism
chemical_list: C115848:AGO1 protein, human; C466422:AGO2 protein, human; D060565:Argonaute Proteins; D039642:Eukaryotic Initiation Factors; D035683:MicroRNAs; D058727:RNA, Small Untranslated; C517918:DROSHA protein, human; D043244:Ribonuclease III