Department of Biochemistry, Molecular Biology and Biophysics, Institute for Molecular Virology, Masonic Cancer Center, and Center for Genome Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA.
J Biol Chem. 2013 Jun 14;288(24):17253-60. doi: 10.1074/jbc.M113.458661. Epub 2013 May 2.
APOBEC3A (A3A) is a myeloid lineage-specific DNA cytosine deaminase with a role in innate immunity to foreign DNA. Previous studies have shown that heterologously expressed A3A is genotoxic, suggesting that monocytes may have a mechanism to regulate this enzyme. Indeed, we observed no significant cytotoxicity when interferon was used to induce the expression of endogenous A3A in CD14(+)-enriched primary cells or the monocytic cell line THP-1. In contrast, doxycycline-induced A3A in HEK293 cells caused major cytotoxicity at protein levels lower than those observed when CD14(+) cells were stimulated with interferon. Immunofluorescent microscopy of interferon-stimulated CD14(+) and THP-1 cells revealed that endogenous A3A is cytoplasmic, in stark contrast to stably or transiently transfected A3A, which has a cell-wide localization. A3A constructs engineered to be cytoplasmic are also nontoxic in HEK293 cells. These data combine to suggest that monocytic cells use a cytoplasmic retention mechanism to control A3A and avert genotoxicity during innate immune responses.
载脂蛋白 B mRNA 编辑酶 3A（APOBEC3A，A3A）是一种具有固有免疫外来 DNA 作用的骨髓谱系特异性 DNA 胞嘧啶脱氨酶。先前的研究表明，异源表达的 A3A 具有遗传毒性，这表明单核细胞可能具有调节这种酶的机制。事实上，当干扰素被用来诱导 CD14(+) 细胞中内源性 A3A 的表达或单核细胞系 THP-1 时，我们没有观察到明显的细胞毒性。相比之下，在 HEK293 细胞中，强力霉素诱导的 A3A 引起的细胞毒性比干扰素刺激 CD14(+)细胞时观察到的要低。用干扰素刺激的 CD14(+)和 THP-1 细胞的免疫荧光显微镜显示，内源性 A3A 是细胞质的，与稳定或瞬时转染的 A3A 形成鲜明对比，后者具有全细胞定位。工程化的细胞质 A3A 构建体在 HEK293 细胞中也没有毒性。这些数据表明，单核细胞利用细胞质保留机制来控制 A3A，并在固有免疫反应期间避免遗传毒性。
