Regulation and Action of APOBEC3G

描述（由申请人提供）：载脂蛋白B mRNA编辑酶，催化多肽-1样3G （APOBEC3G, A3G）对应于宿主衍生的胞苷脱氨酶，具有强大的抗逆转录病毒活性。当被纳入出芽的HIV病毒粒子时，A3G酶在下一个靶细胞中逆转录过程中产生的新生HIV DNA大量突变，从而阻止HIV的生长。HIV通过其Vif基因产物对抗A3G的这些影响，Vif基因产物促进蛋白酶体介导的加速降解和部分受损的A3G从头合成。细胞内A3G的耗竭使抗病毒酶无法整合到子代病毒粒子中。我们最近的研究揭示了A3G在静止CD4 t细胞中的第二种抗病毒作用。在这些t淋巴细胞中，细胞A3G作为一种高活性的进入后限制因子，阻断野生型和三角洲型HIV的生长。目前尚不清楚这种由A3G介导的“抗vif”抗hiv防御是否涉及胞苷脱胺或其他不同的机制。此外，当t细胞被激活时，A3G的这种进入后限制功能丧失的机制仍然不完全清楚。同样，宿主细胞如何保护自己的DNA免受A3G的诱变作用也知之甚少。最后，除了这些抗病毒作用外，A3G是否还具有其他关键功能尚不清楚。在Specific Aim 1中，实验将破译A3G和密切相关的A3F和A3B抗病毒酶是如何在细胞中被调节的。在Specific Aim 2中，A3G作为静止CD4 t细胞进入后限制因子的作用机制、受这种限制影响的病毒范围以及A3F潜在的类似功能将被描述。最后，在Specific Aim 3中，研究将评估A3G是否介导哺乳动物细胞中重要的非抗病毒功能。这些实验将包括制备和分析缺乏A3G基因功能类似物的小鼠。总之，这个实验计划有望丰富我们对A3G生物学以及相关的A3F和A3B酶的理解。有了这样的认识，抑制HIV生长的新治疗策略可能会出现。

DESCRIPTION (provided by applicant): Apolipoprotein B mRNA editing enzyme, catalytic polypeptide-1 like 3G (APOBEC3G, A3G) corresponds to a host-derived cytidine deaminase that displays potent anti-retroviral activity. When incorporated into budding HIV virions, the A3G enzyme massively mutates nascent HIV DNA produced during reverse transcription in the next target cell thereby halting HIV growth. HIV counters these effects of A3G through its Vif gene product, which promotes accelerated proteasome-mediated degradation and partially impaired de novo synthesis of A3G. The intracellular depletion of A3G makes the antiviral enzyme unavailable for incorporation into progeny virions. Our recent studies have unveiled a second antiviral action of A3G operating in resting CD4 T-cells. In these T-lymphocytes, cellular A3G functions as a highly active post-entry restriction factor blocking the growth of both wild type and deltaVif forms of HIV. Whether this "Vif-resistant" anti-HIV defense mediated by A3G involves cytidine deamination or a different mechanism is currently unknown. Further, the mechanism by which this post-entry restricting function of A3G is forfeited when T-cells are activated remains incompletely understood. Similarly, little is known about how host cells safeguard their own DNA from the mutagenic effects of A3G. Finally, it remains unknown whether A3G exerts other key functions beyond these antiviral effects. In Specific Aim 1, experiments will be performed to decipher how A3G and the closely related A3F and A3B antiviral enzymes are regulated in cells. In Specific Aim 2, the mechanism of A3G action as a post-entry restriction factor in resting CD4 T-cells, the range of viruses affected by this restriction, and potential similar functions of A3F will be delineated. Finally, in Specific Aim 3, studies will be conducted to assess whether A3G mediates important non-antiviral functions in mammalian cells. These experiments will involve the preparation and analysis of mice lacking the functional analogue of the A3G gene. Together, this program of proposed experimentation promises to enrich our understanding of the biology of A3G as well as the related A3F and A3B enzymes. With such understanding, new therapeutic strategies for inhibiting HIV growth could emerge.