The human apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3 (APOBEC3, A3) family member proteins can deaminate cytosines in single-strand (ss) DNA, which restricts human immunodeficiency virus type 1 (HIV-1), retrotransposons, and other viruses such as hepatitis B virus, but can cause a mutator phenotype in many cancers. While structural information exists for several A3 proteins, the precise details regarding deamination target selection are not fully understood. Here, we report the first parallel, comparative analysis of site selection of A3 deamination using six of the seven purified A3 member enzymes, oligonucleotides having 5'TC3' or 5'CT3' dinucleotide target sites, and different flanking bases within diverse DNA secondary structures. A3A, A3F and A3H were observed to have strong preferences toward the TC target flanked by A or T, while all examined A3 proteins did not show a preference for a TC target flanked by a G. We observed that the TC target was strongly preferred in ssDNA regions rather than dsDNA, loop or bulge regions, with flanking bases influencing the degree of preference. CT was also shown to be a potential deamination target. Taken together, our observations provide new insights into A3 enzyme target site selection and how A3 mutagenesis impacts mutation rates.

中文翻译：

---

APOBEC3 家族成员中的脱氨基热点由靶位点序列背景和 ssDNA 二级结构定义。


人类载脂蛋白 B mRNA 编辑酶、催化多肽样 3 (APOBEC3、A3) 家族成员蛋白可以使单链 (ss) DNA 中的胞嘧啶脱氨基，从而限制人类免疫缺陷病毒 1 型 (HIV-1)、逆转录转座子和其他病毒乙型肝炎病毒等病毒，但可以在许多癌症中引起突变表型。虽然存在多种 A3 蛋白的结构信息，但有关脱氨靶点选择的精确细节尚未完全了解。在这里，我们报告了使用七种纯化的 A3 成员酶中的六种、具有 5'TC3' 或 5'CT3' 二核苷酸靶位点的寡核苷酸以及不同 DNA 二级结构中不同侧翼碱基的 A3 脱氨基位点选择的首次平行比较分析。观察到 A3A、A3F 和 A3H 对侧翼为 A 或 T 的 TC 靶点具有强烈偏好，而所有检查的 A3 蛋白均未表现出对侧翼为 G 的 TC 靶点的偏好。我们观察到 TC 靶点在单链DNA区域而不是双链DNA、环或凸出区域，侧翼碱基影响偏好程度。 CT 也被证明是一个潜在的脱氨目标。总而言之，我们的观察结果为 A3 酶靶位点选择以及 A3 诱变如何影响突变率提供了新的见解。