Deubiquitinating Enzyme USP21 Inhibits HIV-1 Replication by Downregulating Tat Expression
Deubiquitinating Enzyme USP21 Inhibits HIV-1 Replication by Downregulating Tat Expression
复制标题
去泛素化酶 USP21 通过下调 Tat 表达来抑制 HIV-1 复制。
DOI：
10.1128/jvi.00460-21
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发表时间：
2021-07-01
影响因子：
5.4
通讯作者：
Zhang, Wenyan
中科院分区：
文献类型：
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作者：
Gao, Wenying;Li, Guangquan;Zhang, Wenyan
泛素化在人类免疫缺陷病毒1 （HIV-1）感染中起重要作用。HIV蛋白如Vif和Vpx分别通过蛋白酶体途径介导宿主蛋白APOBEC3和SAMHD1的降解。然而，去泛素化酶是否在HIV-1感染中起重要作用在很大程度上是未知的。在这里，我们证明了去泛素酶USP21通过间接下调HIV-1转录反激活子（Tat）的表达来有效抑制HIV-1的产生，这是HIV-1转录延伸所必需的。USP21通过其去泛素酶活性使Tat去泛素化，但与显性阴性泛素突变体（Ub-KO）相比，USP21降低Tat表达的能力更强，这表明USP21介导的Tat抑制可能有其他机制。进一步的研究表明，USP21通过增加cyclin T1启动子中组蛋白K9的甲基化来下调cyclin T1 mRNA水平，cyclin T1是正转录延伸因子b （P-TEFb）的一个亚基，与Tat和反活化反应元件（TAR）相互作用，是转录刺激和Tat稳定性所必需的。此外，USP21对其他HIV-1附属蛋白（包括Vif、Vpr、Vpx和Vpu）的功能没有影响，表明USP21对Tat具有特异性。这些发现提高了我们对usp21介导的HIV-1产生的功能抑制的理解。泛素化在病毒感染中起重要作用。去泛素化酶（deubiquitination酶，DUBs）通过从靶蛋白上切割泛素来逆转泛素化，从而影响病毒感染。USP家族是dub中最大的亚家族，其成员在HIV-1感染中的作用在很大程度上是未知的。在这里，我们筛选了一系列USP成员，发现USP21通过特异性靶向Tat而不是其他HIV-1辅助蛋白来抑制HIV-1的产生。进一步的研究表明，USP21通过两种方式降低Tat的表达。首先，USP21去泛素化多泛素化Tat，导致Tat不稳定；其次，USP21降低P-TEFb的重要组成部分cyclin T1 （CycT1）的mRNA水平，导致Tat下调。因此，在这项研究中，我们报道了去泛素酶USP21在HIV-1感染中的新作用。USP21代表了开发新型抗hiv药物的潜在有用靶标。
Ubiquitination plays an important role in human immunodeficiency virus 1 (HIV-1) infection. HIV proteins such as Vif and Vpx mediate the degradation of the host proteins APOBEC3 and SAMHD1, respectively, through the proteasome pathway. However, whether deubiquitylating enzymes play an essential role in HIV-1 infection is largely unknown. Here, we demonstrate that the deubiquitinase USP21 potently inhibits HIV-1 production by indirectly downregulating the expression of HIV-1 transactivator of transcription (Tat), which is essential for transcriptional elongation in HIV-1. USP21 deubiquitylates Tat via its deubiquitinase activity, but a stronger ability to reduce Tat expression than a dominant-negative ubiquitin mutant (Ub-KO) showed that other mechanisms may contribute to USP21-mediated inhibition of Tat. Further investigation showed that USP21 downregulates cyclin T1 mRNA levels by increasing methylation of histone K9 in the promoter of cyclin T1, a subunit of the positive transcription elongation factor b (P-TEFb) that interacts with Tat and transactivation response element (TAR) and is required for transcription stimulation and Tat stability. Moreover, USP21 had no effect on the function of other HIV-1 accessory proteins, including Vif, Vpr, Vpx, and Vpu, indicating that USP21 was specific to Tat. These findings improve our understanding of USP21-mediated functional suppression of HIV-1 production.IMPORTANCE Ubiquitination plays an essential role in viral infection. Deubiquitinating enzymes (DUBs) reverse ubiquitination by cleaving ubiquitins from target proteins, thereby affecting viral infection. The role of the members of the USP family, which comprises the largest subfamily of DUBs, is largely unknown in HIV-1 infection. Here, we screened a series of USP members and found that USP21 inhibits HIV-1 production by specifically targeting Tat but not the other HIV-1 accessory proteins. Further investigations revealed that USP21 reduces Tat expression in two ways. First, USP21 deubiquitinates polyubiquitinated Tat, causing Tat instability, and second, USP21 reduces the mRNA levels of cyclin T1 (CycT1), an important component of P-TEFb, that leads to Tat downregulation. Thus, in this study, we report a novel role of the deubiquitinase, USP21, in HIV-1 infection. USP21 represents a potentially useful target for the development of novel anti-HIV drugs.