Yu Qin, König Renate, Pillai Satish, Chiles Kristopher, Kearney Mary, Palmer Sarah, Richman Douglas, Coffin John M, Landau Nathaniel R
Infectious Disease Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, USA.
Nat Struct Mol Biol. 2004 May;11(5):435-42. doi: 10.1038/nsmb758. Epub 2004 Apr 18.
HIV-1 deleted for the vif accessory gene encapsidates the cellular cytidine deaminase APOBEC3G. Upon infection, the encapsidated APOBEC3G induces G-->A mutations in the viral reverse transcripts. The G-->A mutations result either from C-->U deamination of the minus strand or deamination of both strands followed by repair of the plus strand. We report here that minus-strand deamination occurred over the length of the virus genome, preferentially at CCCA sequences, with a graded frequency in the 5'-->3' direction. APOBEC3G induced previously undetected C-->T mutations in the 5' U3 and the primer-binding site, both of which become transiently single-stranded during reverse transcription. In vitro, APOBEC3G bound and deaminated single-stranded DNA (ssDNA) but not double-stranded DNA (dsDNA) or DNA-RNA hybrids. We propose that the requirement for ssDNA accounts for the minus-strand mutations, the 5'-->3' graded frequency of deamination and the rare C-->T mutations.
缺失病毒感染性因子（vif）辅助基因的HIV-1会包裹细胞胞苷脱氨酶载脂蛋白B mRNA编辑酶催化多肽样3G（APOBEC3G）。感染时，被包裹的APOBEC3G会在病毒逆转录产物中诱导G→A突变。G→A突变要么源于负链的C→U脱氨基作用，要么源于两条链的脱氨基作用，随后正链进行修复。我们在此报告，负链脱氨基作用发生在病毒基因组全长范围内，优先发生于CCCA序列，在5'→3'方向上频率呈梯度变化。APOBEC3G在5' U3和引物结合位点诱导了之前未检测到的C→T突变，这两个区域在逆转录过程中都会短暂形成单链。在体外，APOBEC3G能结合并使单链DNA（ssDNA）脱氨基，但不能使双链DNA（dsDNA）或DNA-RNA杂交体脱氨基。我们推测，对ssDNA的需求解释了负链突变、5'→3'脱氨基频率梯度以及罕见的C→T突变现象。
