Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA.
Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA.
Nat Microbiol. 2018 Dec;3(12):1354-1361. doi: 10.1038/s41564-018-0256-x. Epub 2018 Oct 8.
Host factors that silence provirus transcription in CD4 memory T cells help HIV-1 escape eradication by the host immune system and by antiviral drugs. These same factors, however, must be overcome for HIV-1 to propagate. Here we show that Vpx and Vpr encoded by diverse primate immunodeficiency viruses activate provirus transcription. Vpx and Vpr are adaptor proteins for the DCAF1-CUL4A/B E3 ubiquitin ligase that degrade SAMHD1 and increase reverse transcription. Nonetheless, Vpx and Vpr have effects on reporter gene expression that are not explained by SAMHD1 degradation. A screen for factors that mimic these effects identified the human silencing hub (HUSH) complex, FAM208A (TASOR/RAP140), MPHOSPH8 (MPP8), PPHLN1 (PERIPHILIN) and MORC2. Vpx associated with the HUSH complex and decreased steady-state level of these proteins in a DCAF1/CUL4A/B/proteasome-dependent manner. Replication kinetics of HIV-1 and SIV was accelerated to a similar extent by vpx or FAM208A knockdown. Finally, vpx increased steady-state levels of LINE-1 ORF1p, as previously described for FAM208A disruption. These results demonstrate that the HUSH complex represses primate immunodeficiency virus transcription, and that, to counteract this restriction, viral Vpx or Vpr proteins degrade the HUSH complex.
宿主因素可使 CD4 记忆 T 细胞中的前病毒转录沉默，从而帮助 HIV-1 逃避宿主免疫系统和抗病毒药物的清除。然而，为了让 HIV-1 得以复制，这些相同的因素必须被克服。在这里，我们发现不同灵长类免疫缺陷病毒编码的 Vpx 和 Vpr 可激活前病毒转录。Vpx 和 Vpr 是用于 DCAF1-CUL4A/B E3 泛素连接酶的衔接蛋白，可降解 SAMHD1 并增加逆转录。尽管如此，Vpx 和 Vpr 对报告基因表达的影响并不能用 SAMHD1 的降解来解释。筛选出模拟这些效应的因子，鉴定出了人类沉默枢纽（HUSH）复合物、FAM208A（TASOR/RAP140）、MPHOSPH8（MPP8）、PPHLN1（PERIPHILIN）和 MORC2。Vpx 与 HUSH 复合物相关，并以 DCAF1/CUL4A/B/蛋白酶体依赖的方式降低这些蛋白质的稳态水平。HIV-1 和 SIV 的复制动力学在 vpx 或 FAM208A 敲低的情况下被类似地加速。最后，vpx 增加了 LINE-1 ORF1p 的稳态水平，正如 FAM208A 破坏所描述的那样。这些结果表明，HUSH 复合物抑制灵长类免疫缺陷病毒转录，而病毒 Vpx 或 Vpr 蛋白降解 HUSH 复合物以对抗这种限制。
