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Abstract：
TRIM5α is a type I interferon-stimulated anti-retroviral restriction factor expressed in most primates and homologous proteins are expressed in other mammals. Through its C-terminal PRYSPRY (B30.2) domain, TRIM5α binds to incoming and intact post-fusion retroviral cores in the cytoplasm. Following this direct interaction, the retroviral capsid core is destabilized and progression of the virus life cycle is interrupted. Specific recognition of its viral target by TRIM5α also triggers the induction of an antiviral state involving the activation of transcription factors NF-κB- and AP-1. In addition to PRYSPRY, several other TRIM5α domains are important for anti-retroviral function, including a RING zinc-binding motif. This domain has \"E3\" ubiquitin ligase activity and is involved in both the direct inhibition of incoming retroviruses and innate immune activation. A highly conserved sumoylation consensus site is present between the RING motif and the N-terminal extremity of TRIM5α. No clear role in restriction has been mapped to this sumoylation site, and no sumoylated forms of TRIM5α have been observed. Here we confirm that mutating the putatively sumoylated lysine (K10) of the Rhesus macaque TRIM5α (TRIM5αRh) to an arginine has only a small effect on restriction. However, we show that the mutation significantly decreases the TRIM5α-induced generation of free K63-linked ubiquitin chains, an intermediate in the activation of innate immunity pathways. Accordingly, K10R decreases TRIM5α-mediated activation of both NF-κB and AP-1. Concomitantly, we find that K10R causes a large increase in the levels of ubiquitylated TRIM5α. Finally, treatment with the nuclear export inhibitor leptomycin B shows that K10R enhances the nuclear localization of TRIM5αRh, while at the same time reducing its level of association with nuclear SUMO bodies. In conclusion, the TRIM5α sumoylation site appears to modulate the E3 ubiquitin ligase activities of the adjacent RING domain, promoting K63-linked ubiquitin chains at the expense of auto-ubiquitylation which is probably K48-linked. Consistently, we find this sumoylation site to be important for innate immune activation by TRIM5α. In addition, lysine 10 regulates TRIM5α nuclear shuttling and nuclear localization, which may also be related to its role in innate immunity activation.
摘要：
TRIM5α是在大多数灵长类动物中表达的I型干扰素刺激的抗逆转录病毒限制因子,并且同源蛋白在其他哺乳动物中表达。通过其C端PRYSPRY（B30.2）结构域，TRIM5α与细胞质中传入的和完整的融合后逆转录病毒核心结合。在这种直接互动之后，逆转录病毒衣壳核心不稳定，病毒生命周期的进展中断。TRIM5α对其病毒靶标的特异性识别还触发了涉及转录因子NF-κB-和AP-1激活的抗病毒状态的诱导。除了PRYSPRY,其他几个TRIM5α结构域对于抗逆转录病毒功能很重要，包括一个环锌结合图案。该结构域具有“E3”泛素连接酶活性，并参与直接抑制传入的逆转录病毒和先天免疫激活。在RING基序和TRIM5α的N末端末端之间存在一个高度保守的sumoylation共有位点。在这个sumoylation位点没有明确的限制作用，并且没有观察到TRIM5α的磺酰化形式。在这里，我们确认将恒河猴TRIM5α（TRIM5αRh）的推定的磺酰化赖氨酸（K10）突变为精氨酸对限制仅有很小的影响。然而,我们表明，突变显著减少TRIM5α诱导的游离K63连接的泛素链的产生，先天免疫途径激活的中间体。因此，K10R降低TRIM5α介导的NF-κB和AP-1的活化。同时，我们发现K10R导致泛素化TRIM5α的水平大幅增加。最后,用核输出抑制剂leptom霉素B治疗表明K10R增强了TRIM5αRh的核定位，同时降低其与核SUMO机构的联系水平。总之,TRIM5α上调位点似乎调节邻近RING结构域的E3泛素连接酶活性，以可能是K48连接的自动泛素化为代价促进K63连接的泛素链。始终如一，我们发现这个sumoylation位点对TRIM5α的先天免疫激活很重要。此外,赖氨酸10调节TRIM5α核穿梭和核定位，这也可能与其在先天免疫激活中的作用有关。
