title: Monomeric APOBEC3G is catalytically active and has antiviral activity.
abstract: APOBEC3G (APO3G) is a cytidine deaminase that restricts replication of vif-defective human immunodeficiency virus type 1 (HIV-1). Like other members of the cellular deaminase family, APO3G has the propensity to form homo-multimers. In the current study, we investigated the functional determinants for multimerization of human APO3G and studied the role of APO3G multimerization for catalytic activity, virus encapsidation, and antiviral activity. We found that human APO3G is capable of forming multimeric complexes in transfected HeLa cells. Interestingly, multimerization of APO3G was exquisitely sensitive to RNase treatment, suggesting that interaction of APO3G subunits is facilitated or stabilized by an RNA bridge. Mutation of a conserved cysteine residue (C97) that is part of an N-terminal zinc-finger motif in APO3G abolished multimerization of APO3G; however, the C97 mutation inhibited neither in vitro deaminase activity nor antiviral function of APO3G. These results suggest that monomeric APO3G is both catalytically active and has antiviral activity. Interference studies employing either catalytically inactive or packaging-incompetent APO3G variants suggest that wild-type APO3G is packaged into HIV-1 particles in monomeric form. These results provide novel insights into the catalytic function and antiviral property of APO3G and demonstrate an important role for C97 in the RNA-dependent multimerization of this protein.
authors.affiliation: Laboratory of Molecular Microbiology, Viral Biochemistry Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-0460, USA.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Opi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Takeuchi
authors.forename: Sandra
authors.initials: S
authors.lastname: Kao
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Khan
authors.forename: Eri
authors.initials: E
authors.lastname: Miyagi
authors.forename: Ritu
authors.initials: R
authors.lastname: Goila-Gaur
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Iwatani
authors.forename: Judith G
authors.initials: JG
authors.lastname: Levin
authors.forename: Klaus
authors.initials: K
authors.lastname: Strebel
mesh_terms: D000071480:APOBEC-3G Deaminase; D019943:Amino Acid Substitution / Q000235:genetics; D000998:Antiviral Agents / Q000378:metabolism / Q000494:pharmacology*; D020134:Catalytic Domain / Q000235:genetics; D003545:Cysteine / Q000235:genetics; D003564:Cytidine Deaminase; D015497:HIV-1 / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D009700:Nucleoside Deaminases / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D012097:Repressor Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D012260:Ribonucleases / Q000494:pharmacology; D019065:Virus Assembly / Q000502:physiology*
chemical_list: D000998:Antiviral Agents; D012097:Repressor Proteins; D012260:Ribonucleases; D009700:Nucleoside Deaminases; D000071480:APOBEC-3G Deaminase; C464924:APOBEC3G protein, human; D003564:Cytidine Deaminase; D003545:Cysteine