title: The ribonuclease activity of SAMHD1 is required for HIV-1 restriction.
abstract: The HIV-1 restriction factor SAM domain- and HD domain-containing protein 1 (SAMHD1) is proposed to inhibit HIV-1 replication by depleting the intracellular dNTP pool. However, phosphorylation of SAMHD1 regulates its ability to restrict HIV-1 without decreasing cellular dNTP levels, which is not consistent with a role for SAMHD1 dNTPase activity in HIV-1 restriction. Here, we show that SAMHD1 possesses RNase activity and that the RNase but not the dNTPase function is essential for HIV-1 restriction. By enzymatically characterizing Aicardi-Goutières syndrome (AGS)-associated SAMHD1 mutations and mutations in the allosteric dGTP-binding site of SAMHD1 for defects in RNase or dNTPase activity, we identify SAMHD1 point mutants that cause loss of one or both functions. The RNase-positive and dNTPase-negative SAMHD1D137N mutant is able to restrict HIV-1 infection, whereas the RNase-negative and dNTPase-positive SAMHD1Q548A mutant is defective for HIV-1 restriction. SAMHD1 associates with HIV-1 RNA and degrades it during the early phases of cell infection. SAMHD1 silencing in macrophages and CD4(+) T cells from healthy donors increases HIV-1 RNA stability, rendering the cells permissive for HIV-1 infection. Furthermore, phosphorylation of SAMHD1 at T592 negatively regulates its RNase activity in cells and impedes HIV-1 restriction. Our results reveal that the RNase activity of SAMHD1 is responsible for preventing HIV-1 infection by directly degrading the HIV-1 RNA.
authors.affiliation: 1] Creative Research Initiative Center for Antigen Presentation, Seoul National University, Seoul, Republic of Korea. [2] Department of the Interdisciplinary Program in Genetic Engineering, Seoul National University, Seoul, Republic of Korea.
authors.forename: Jeongmin
authors.initials: J
authors.lastname: Ryoo
authors.affiliation: 1] Creative Research Initiative Center for Antigen Presentation, Seoul National University, Seoul, Republic of Korea. [2] Department of Biological Sciences, Seoul National University, Seoul, Republic of Korea.
authors.forename: Jongsu
authors.initials: J
authors.lastname: Choi
authors.affiliation: 1] Creative Research Initiative Center for Antigen Presentation, Seoul National University, Seoul, Republic of Korea. [2] Department of the Interdisciplinary Program in Genetic Engineering, Seoul National University, Seoul, Republic of Korea.
authors.forename: Changhoon
authors.initials: C
authors.lastname: Oh
authors.affiliation: 1] Creative Research Initiative Center for Antigen Presentation, Seoul National University, Seoul, Republic of Korea. [2] Department of Biological Sciences, Seoul National University, Seoul, Republic of Korea.
authors.forename: Sungchul
authors.initials: S
authors.lastname: Kim
authors.affiliation: 1] Creative Research Initiative Center for Antigen Presentation, Seoul National University, Seoul, Republic of Korea. [2] Department of Biological Sciences, Seoul National University, Seoul, Republic of Korea.
authors.forename: Minji
authors.initials: M
authors.lastname: Seo
authors.affiliation: 1] Creative Research Initiative Center for Antigen Presentation, Seoul National University, Seoul, Republic of Korea. [2] Department of Biological Sciences, Seoul National University, Seoul, Republic of Korea.
authors.forename: Seok-Young
authors.initials: SY
authors.lastname: Kim
authors.affiliation: Department of Biological Sciences, Seoul National University, Seoul, Republic of Korea.
authors.forename: Daekwan
authors.initials: D
authors.lastname: Seo
authors.affiliation: 1] Department of Biological Sciences, Seoul National University, Seoul, Republic of Korea. [2] Center for RNA Research, Institute for Basic Science, Seoul, Republic of Korea.
authors.forename: Jongkyu
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA.
authors.forename: Tommy E
authors.initials: TE
authors.lastname: White
authors.affiliation: Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA.
authors.forename: Alberto
authors.initials: A
authors.lastname: Brandariz-Nuñez
authors.affiliation: Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA.
authors.forename: Felipe
authors.initials: F
authors.lastname: Diaz-Griffero
authors.affiliation: Department of Agricultural Biotechnology, Seoul National University, Seoul, Republic of Korea.
authors.forename: Cheol-Heui
authors.initials: CH
authors.lastname: Yun
authors.affiliation: Center for Drug Discovery, Department of Pediatrics, Emory School of Medicine, Atlanta, Georgia, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Hollenbaugh
authors.affiliation: 1] Center for Drug Discovery, Department of Pediatrics, Emory School of Medicine, Atlanta, Georgia, USA. [2] School of Pharmacy, Kyung Hee University, Seoul, Republic of Korea.
authors.forename: Baek
authors.initials: B
authors.lastname: Kim
authors.affiliation: 1] Department of Biological Sciences, Seoul National University, Seoul, Republic of Korea. [2] Center for RNA Research, Institute for Basic Science, Seoul, Republic of Korea. [3] Bioinformatics Institute, Seoul National University, Seoul, Republic of Korea.
authors.forename: Daehyun
authors.initials: D
authors.lastname: Baek
authors.affiliation: 1] Creative Research Initiative Center for Antigen Presentation, Seoul National University, Seoul, Republic of Korea. [2] Department of Biological Sciences, Seoul National University, Seoul, Republic of Korea.
authors.forename: Kwangseog
authors.initials: K
authors.lastname: Ahn
mesh_terms: D020274:Autoimmune Diseases of the Nervous System / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D015496:CD4-Positive T-Lymphocytes; D045744:Cell Line, Tumor; D015658:HIV Infections / Q000235:genetics / Q000821:virology*; D015497:HIV-1 / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008264:Macrophages; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation; D009421:Nervous System Malformations / Q000235:genetics; D010766:Phosphorylation; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism*; D012260:Ribonucleases / Q000378:metabolism; D000076106:SAM Domain and HD Domain-Containing Protein 1; D017423:Sequence Analysis, RNA; D014779:Virus Replication
chemical_list: D034741:RNA, Small Interfering; D012367:RNA, Viral; D012260:Ribonucleases; D000076106:SAM Domain and HD Domain-Containing Protein 1; C484280:SAMHD1 protein, human; D020559:Monomeric GTP-Binding Proteins