title: Binding of RNA by APOBEC3G controls deamination-independent restriction of retroviruses.
abstract: APOBEC3G (A3G) is a host-encoded protein that potently restricts the infectivity of a broad range of retroviruses. This can occur by mechanisms dependent on catalytic activity, resulting in the mutagenic deamination of nascent viral cDNA, and/or by other means that are independent of its catalytic activity. It is not yet known to what extent deamination-independent processes contribute to the overall restriction, how they exactly work or how they are regulated. Here, we show that alanine substitution of either tryptophan 94 (W94A) or 127 (W127A) in the non-catalytic N-terminal domain of A3G severely impedes RNA binding and alleviates deamination-independent restriction while still maintaining DNA mutator activity. Substitution of both tryptophans (W94A/W127A) produces a more severe phenotype in which RNA binding and RNA-dependent protein oligomerization are completely abrogated. We further demonstrate that RNA binding is specifically required for crippling late reverse transcript accumulation, preventing proviral DNA integration and, consequently, restricting viral particle release. We did not find that deaminase activity made a significant contribution to the restriction of any of these processes. In summary, this work reveals that there is a direct correlation between A3G's capacity to bind RNA and its ability to inhibit retroviral infectivity in a deamination-independent manner.
authors.affiliation: Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, Emerging Pathogens Research Centre, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5 and Department of Pathology and Laboratory Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5.
authors.forename: Kasandra
authors.initials: K
authors.lastname: Bélanger
authors.forename: Mathieu
authors.initials: M
authors.lastname: Savoie
authors.forename: María Carla
authors.initials: MC
authors.lastname: Rosales Gerpe
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Couture
authors.forename: Marc-André
authors.initials: MA
authors.lastname: Langlois
mesh_terms: D000071478:APOBEC Deaminases; D000409:Alanine / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D020134:Catalytic Domain; D003564:Cytidine Deaminase; D043525:Cytosine Deaminase / Q000235:genetics / Q000378:metabolism*; D003641:Deamination; D004789:Enzyme Activation; D057809:HEK293 Cells; D015497:HIV-1 / Q000502:physiology; D006801:Humans; D051379:Mice; D008979:Moloney murine leukemia virus / Q000502:physiology*; D041681:NIH 3T3 Cells; D055503:Protein Multimerization; D012367:RNA, Viral / Q000235:genetics*; D048348:Reverse Transcription; D014364:Tryptophan / Q000235:genetics / Q000378:metabolism; D019065:Virus Assembly; D016662:Virus Integration; D057074:Virus Release
chemical_list: D012367:RNA, Viral; D014364:Tryptophan; D043525:Cytosine Deaminase; D000071478:APOBEC Deaminases; C502889:APOBEC3 proteins, human; D003564:Cytidine Deaminase; D000409:Alanine