Life Sciences Institute, University of Michigan, Ann Arbor, MI, 48109, USA.
Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA.
Nat Commun. 2017 Oct 18;8(1):1021. doi: 10.1038/s41467-017-01309-6.
The APOBEC3 family of cytidine deaminases cause lethal hypermutation of retroviruses via deamination of newly reverse-transcribed viral DNA. Their ability to bind RNA is essential for virion infiltration and antiviral activity, yet the mechanisms of viral RNA recognition are unknown. By screening naturally occurring, polymorphic, non-human primate APOBEC3H variants for biological and crystallization properties, we obtained a 2.24-Å crystal structure of pig-tailed macaque APOBEC3H with bound RNA. Here, we report that APOBEC3H forms a dimer around a short RNA duplex and, despite the bound RNA, has potent cytidine deaminase activity. The structure reveals an unusual RNA-binding mode in which two APOBEC3H molecules at opposite ends of a seven-base-pair duplex interact extensively with both RNA strands, but form no protein-protein contacts. CLIP-seq analysis revealed that APOBEC3H preferentially binds to sequences in the viral genome predicted to contain duplexes, a property that may facilitate both virion incorporation and catalytic activity.
APOBEC3 家族的胞嘧啶脱氨酶通过脱氨新逆转录的病毒 DNA 导致逆转录病毒的致死性超突变。它们结合 RNA 的能力对于病毒粒子的渗透和抗病毒活性是必需的，但病毒 RNA 识别的机制尚不清楚。通过筛选天然存在的、多态的、非人类灵长类 APOBEC3H 变体的生物学和结晶特性，我们获得了与 RNA 结合的猪尾猕猴 APOBEC3H 的 2.24 Å 晶体结构。在这里，我们报告 APOBEC3H 围绕短 RNA 双链形成二聚体，并且尽管结合了 RNA，但仍具有有效的胞嘧啶脱氨酶活性。该结构揭示了一种不寻常的 RNA 结合模式，其中双链体两端的两个 APOBEC3H 分子与两条 RNA 链广泛相互作用，但不形成任何蛋白质-蛋白质接触。CLIP-seq 分析表明 APOBEC3H 优先结合预测含有双链体的病毒基因组序列，这一特性可能有助于病毒粒子的掺入和催化活性。
