title: DNA mutagenic activity and capacity for HIV-1 restriction of the cytidine deaminase APOBEC3G depend on whether DNA or RNA binds to tyrosine 315.
abstract: APOBEC3G (A3G) belongs to the AID/APOBEC protein family of cytidine deaminases (CDA) that bind to nucleic acids. A3G mutates the HIV genome by deamination of dC to dU, leading to accumulation of virus-inactivating mutations. Binding to cellular RNAs inhibits A3G binding to substrate single-stranded (ss) DNA and CDA activity. Bulk RNA and substrate ssDNA bind to the same three A3G tryptic peptides (amino acids 181-194, 314-320, and 345-374) that form parts of a continuously exposed protein surface extending from the catalytic domain in the C terminus of A3G to its N terminus. We show here that the A3G tyrosines 181 and 315 directly cross-linked ssDNA. Binding experiments showed that a Y315A mutation alone significantly reduced A3G binding to both ssDNA and RNA, whereas Y181A and Y182A mutations only moderately affected A3G nucleic acid binding. Consistent with these findings, the Y315A mutant exhibited little to no deaminase activity in anEscherichia coliDNA mutator reporter, whereas Y181A and Y182A mutants retained ∼50% of wild-type A3G activity. The Y315A mutant also showed a markedly reduced ability to assemble into viral particles and had reduced antiviral activity. In uninfected cells, the impaired RNA-binding capacity of Y315A was evident by a shift of A3G from high-molecular-mass ribonucleoprotein complexes to low-molecular-mass complexes. We conclude that Tyr-315 is essential for coordinating ssDNA interaction with or entry to the deaminase domain and hypothesize that RNA bound to Tyr-315 may be sufficient to competitively inhibit ssDNA deaminase-dependent antiviral activity.
authors.affiliation: From the Departments of Biochemistry and Biophysics and.|Center for RNA Biology, and.
authors.forename: Bogdan
authors.initials: B
authors.lastname: Polevoda
authors.affiliation: From the Departments of Biochemistry and Biophysics and.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Joseph
authors.affiliation: Pediatrics.
authors.forename: Alan E
authors.initials: AE
authors.lastname: Friedman
authors.affiliation: OyaGen, Inc., Rochester, New York 14623.
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Bennett
authors.affiliation: From the Departments of Biochemistry and Biophysics and.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Greiner
authors.affiliation: From the Departments of Biochemistry and Biophysics and.
authors.forename: Thareendra
authors.initials: T
authors.lastname: De Zoysa
authors.affiliation: OyaGen, Inc., Rochester, New York 14623.
authors.forename: Ryan A
authors.initials: RA
authors.lastname: Stewart
authors.affiliation: From the Departments of Biochemistry and Biophysics and harold.smith@rochester.edu.|Center for RNA Biology, and.|OyaGen, Inc., Rochester, New York 14623.|Center for AIDS Research, University of Rochester Medical Center, Rochester, New York 14642 and.
authors.forename: Harold C
authors.initials: HC
authors.lastname: Smith
mesh_terms: D000071480:APOBEC-3G Deaminase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019943:Amino Acid Substitution; D002460:Cell Line; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015658:HIV Infections / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D016296:Mutagenesis; D020125:Mutation, Missense; D000072417:Protein Domains; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014443:Tyrosine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D004277:DNA, Single-Stranded; D004279:DNA, Viral; D012367:RNA, Viral; D014443:Tyrosine; D000071480:APOBEC-3G Deaminase; C464924:APOBEC3G protein, human
keywords: APOBEC; DNA binding protein; HIV; RNA; RNA binding protein; cytidine deaminase; human immunodeficiency virus (HIV); mass spectrometry (MS); protein cross-linking