title: APOBEC3 multimerization correlates with HIV-1 packaging and restriction activity in living cells.
abstract: APOBEC3G belongs to a family of DNA cytosine deaminases that are involved in the restriction of a broad number of retroviruses including human immunodeficiency virus type 1 (HIV-1). Prior studies have identified two distinct mechanistic steps in Vif-deficient HIV-1 restriction: packaging into virions and deaminating viral cDNA. APOBEC3A, for example, although highly active, is not packaged and is therefore not restrictive. APOBEC3G, on the other hand, although having weaker enzymatic activity, is packaged into virions and is strongly restrictive. Although a number of studies have described the propensity for APOBEC3 oligomerization, its relevance to HIV-1 restriction remains unclear. Here, we address this problem by examining APOBEC3 oligomerization in living cells using molecular brightness analysis. We find that APOBEC3G forms high-order multimers as a function of protein concentration. In contrast, APOBEC3A, APOBEC3C and APOBEC2 are monomers at all tested concentrations. Among other members of the APOBEC3 family, we show that the multimerization propensities of APOBEC3B, APOBEC3D, APOBEC3F and APOBEC3H (haplotype II) bear more resemblance to APOBEC3G than to APOBEC3A/3C/2. Prior studies have shown that all of these multimerizing APOBEC3 proteins, but not the monomeric family members, have the capacity to package into HIV-1 particles and restrict viral infectivity. This correlation between oligomerization and restriction is further evidenced by two different APOBEC3G mutants, which are each compromised for multimerization, packaging and HIV-1 restriction. Overall, our results imply that multimerization of APOBEC3 proteins may be related to the packaging mechanism and ultimately to virus restriction.
authors.affiliation: School of Physics and Astronomy, University of Minnesota, 116 Church Street Southeast, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA.
authors.forename: Jinhui
authors.initials: J
authors.lastname: Li
authors.affiliation: School of Physics and Astronomy, University of Minnesota, 116 Church Street Southeast, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA; Department of Biochemistry, Molecular Biology and Biophysics, 321 Church Street Southeast, Minneapolis, MN 55455, USA.
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.affiliation: Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA; Department of Biochemistry, Molecular Biology and Biophysics, 321 Church Street Southeast, Minneapolis, MN 55455, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Carpenter
authors.affiliation: Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA; Department of Biochemistry, Molecular Biology and Biophysics, 321 Church Street Southeast, Minneapolis, MN 55455, USA.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: McDougle
authors.affiliation: Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA; Department of Biochemistry, Molecular Biology and Biophysics, 321 Church Street Southeast, Minneapolis, MN 55455, USA.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Luengas
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, 312 Church Street Southeast, Minneapolis, MN 55455, USA.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Macdonald
authors.affiliation: Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA; Department of Biochemistry, Molecular Biology and Biophysics, 321 Church Street Southeast, Minneapolis, MN 55455, USA.
authors.forename: Reuben S
authors.initials: RS
authors.lastname: Harris
authors.affiliation: School of Physics and Astronomy, University of Minnesota, 116 Church Street Southeast, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA; Department of Biomedical Engineering, University of Minnesota, 312 Church Street Southeast, Minneapolis, MN 55455, USA. Electronic address: Mueller@physics.umn.edu.
authors.forename: Joachim D
authors.initials: JD
authors.lastname: Mueller
mesh_terms: D000071478:APOBEC Deaminases; D003564:Cytidine Deaminase; D043525:Cytosine Deaminase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015658:HIV Infections / Q000276:immunology* / Q000378:metabolism / Q000821:virology; D015497:HIV-1 / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D055503:Protein Multimerization; D014771:Virion / Q000378:metabolism; D019065:Virus Assembly / Q000502:physiology*; D014779:Virus Replication / Q000276:immunology*; D054320:vif Gene Products, Human Immunodeficiency Virus / Q000172:deficiency*
chemical_list: D054320:vif Gene Products, Human Immunodeficiency Virus; D043525:Cytosine Deaminase; D000071478:APOBEC Deaminases; C502889:APOBEC3 proteins, human; D003564:Cytidine Deaminase
keywords: APOBEC3G; brightness; fluorescence fluctuation spectroscopy; mobility; molecular mass complex