Natural Polymorphisms and Oligomerization of Human APOBEC3H Contribute to Single-stranded DNA Scanning Ability
Natural Polymorphisms and Oligomerization of Human APOBEC3H Contribute to Single-stranded DNA Scanning Ability
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DOI：
10.1074/jbc.m115.666065
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发表时间：
2015-11-06
影响因子：
4.8
通讯作者：
Chelico, Linda
中科院分区：
文献类型：
--
作者：
Feng, Yuqing;Love, Robin P.;Chelico, Linda
APOBEC 3 H是一种脱氧胞苷脱氨酶，可以在不存在诱导细胞中APOBEC 3 H降解的病毒蛋白Vif的情况下限制HIV-1的复制。APOBEC 3 H在人类中以七种单倍型（I-VII）存在，具有不同的细胞稳定性。在三种稳定的APOBEC 3 H单倍型（II、V和VII）中，单倍型II和V在人群中出现频率最高。尽管APOBEC 3 H是一个真正的限制性因子，但APOBEC 3 H单倍型的比较生物化学表征还没有。我们的特点是单倍型II和V的ssDNA扫描机制，用于搜索其ssDNA底物的胞嘧啶含脱氨基基序。APOBEC 3 H单倍型II能够通过滑动、跳跃和节段间转移运动，在单一酶-底物接触中procrystaldeaminate多个胞嘧啶。与此相反，APOBEC 3 H单倍型V表现出减弱的滑动和片段间转移能力，但能够沿沿着ssDNA跳跃。由于氨基酸178处的Asp或Glu区分这些APOBEC 3 H单倍型，数据表明螺旋6上的该氨基酸有助于持续合成能力。APOBEC 3 H单倍型V的持续合成能力降低并没有导致单循环感染性试验中限制HIV-1复制的效率降低，这表明跳跃和节段间转移对致突变效率的贡献存在冗余。ssDNA上的最佳持续合成能力还需要APOBEC 3 H通过2条链的二聚化。这些发现支持了一个模型，其中跳跃可以弥补节段间转移的缺陷，并表明APOBEC 3 H单倍型II和V有效地诱导HIV-1突变，但通过不同的机制。
APOBEC3H is a deoxycytidine deaminase that can restrict the replication of HIV-1 in the absence of the viral protein Vif that induces APOBEC3H degradation in cells. APOBEC3H exists in humans as seven haplotypes (I-VII) with different cellular stabilities. Of the three stable APOBEC3H haplotypes (II, V, and VII), haplotypes II and V occur most frequently in the population. Despite APOBEC3H being a bona fide restriction factor, there has been no comparative biochemical characterization of APOBEC3H haplotypes. We characterized the ssDNA scanning mechanisms that haplotypes II and V use to search their ssDNA substrate for cytosine-containing deamination motifs. APOBEC3H haplotype II was able to processively deaminate multiple cytosines in a single enzyme-substrate encounter by using sliding, jumping, and intersegmental transfer movements. In contrast, APOBEC3H haplotype V exhibited diminished sliding and intersegmental transfer abilities but was able to jump along ssDNA. Due to an Asp or Glu at amino acid 178 differentiating these APOBEC3H haplotypes, the data indicated that this amino acid on helix 6 contributes to processivity. The diminished processivity of APOBEC3H haplotype V did not result in a reduced efficiency to restrict HIV-1 replication in single-cycle infectivity assays, suggesting a redundancy in the contributions of jumping and intersegmental transfer to mutagenic efficiency. Optimal processivity on ssDNA also required dimerization of APOBEC3H through the 2 strands. The findings support a model in which jumping can compensate for deficiencies in intersegmental transfer and suggest that APOBEC3H haplotypes II and V induce HIV-1 mutagenesis efficiently but by different mechanisms.