Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA.
Biochem Biophys Res Commun. 2011 Sep 9;412(4):612-7. doi: 10.1016/j.bbrc.2011.08.009. Epub 2011 Aug 11.
APOBEC3G (A3G) is a deoxycytidine deaminase active on ssDNA substrates. In HIV infected cells A3G interacted with reverse transcription complexes where its activity as a deoxycytidine deaminase led to mutation of the viral genome. A3G not only bound ssDNA, but it also had an intrinsic ability to bind RNA. In many cell types that can support HIV replication, A3G ssDNA deaminase activity was suppressed and the enzyme resided in high molecular mass, ribonucleoprotein complexes associated with cytoplasmic P-bodies and stress granules. Using a defined in vitro system, we show that RNA alone was sufficient to suppress A3G deaminase activity and did so in an RNA concentration-dependent manner. RNAs of diverse sequences and as short as 25nt were effective inhibitors. Native PAGE analyses showed that RNA formed ribonucleoprotein complexes with A3G and in so doing prevented ssDNA substrates from binding to A3G. The data provided direct evidence that A3G binding to cellular RNAs constituted a substantial impediment to the enzyme's ability to interact with ssDNA.
APOBEC3G（A3G）是一种在 ssDNA 底物上具有脱氨酶活性的脱氧胞苷脱氨酶。在 HIV 感染的细胞中，A3G 与逆转录复合物相互作用，其脱氨酶活性导致病毒基因组发生突变。A3G 不仅结合 ssDNA，还具有内在结合 RNA 的能力。在许多能够支持 HIV 复制的细胞类型中，A3G 的 ssDNA 脱氨酶活性受到抑制，该酶存在于与细胞质 P 体和应激颗粒相关的高分子质量核糖核蛋白复合物中。使用定义明确的体外系统，我们表明 RNA 本身足以抑制 A3G 脱氨酶活性，并且以 RNA 浓度依赖性的方式进行。具有不同序列和短至 25nt 的 RNA 都是有效的抑制剂。天然 PAGE 分析表明，RNA 与 A3G 形成核糖核蛋白复合物，从而阻止 ssDNA 底物与 A3G 结合。这些数据提供了直接证据，表明 A3G 与细胞 RNA 的结合构成了对该酶与 ssDNA 相互作用能力的重大障碍。
