Interfering Residues Narrow the Spectrum of MLV Restriction by Human TRIM5α

TRIM5α is a restriction factor that limits infection of human cells by so-called N- but not B- or NB-tropic strains of murine leukemia virus (MLV). Here, we performed a mutation-based functional analysis of TRIM5α-mediated MLV restriction. Our results reveal that changes at tyrosine³³⁶ of human TRIM5α, within the variable region 1 of its C-terminal PRYSPRY domain, can expand its activity to B-MLV and to the NB-tropic Moloney MLV. Conversely, we demonstrate that the escape of MLV from restriction by wild-type or mutant forms of huTRIM5α can be achieved through interdependent changes at positions 82, 109, 110, and 117 of the viral capsid. Together, our results support a model in which TRIM5α-mediated retroviral restriction results from the direct binding of the antiviral PRYSPRY domain to the viral capsid, and can be prevented by interferences exerted by critical residues on either one of these two partners.     

Hsp70 Interacts with the Retroviral Restriction Factor TRIM5�� and Assists the Folding of TRIM5��

Tripartite motif (TRIM) protein TRIM5α has been shown to restrict human immunodeficiency virus, type 1 infection in Old World monkey cells at the early post-entry step by poorly understood mechanisms. Currently, the physiological function of TRIM5α is not known. In this study, we showed that transiently overexpressed TRIM5α causes a morphological change in HEK293T cells. A proteomics analysis of the protein complexes that were pulled down with hemagglutinin-tagged TRIM5α suggested that the heat shock protein 70 (Hsp70) may serve as a TRIM5α-binding partner. The interaction between Hsp70 and TRIM5α was confirmed by co-localization and co-immunoprecipitation assays. Co-expression of Hsp70 reversed the TRIM5α-induced morphological change in HEK293T cells. Another heat shock protein Hsc70 also bound to TRIM5α, but unlike Hsp70, Hsc70 was not able to reverse the TRIM5α-induced morphological change, suggesting that Hsp70 specifically reverses the morphological change caused by TRIM5α. Studies using a series of TRIM5α deletion mutants demonstrate that, although the PRYSPRY domain is critical for binding to Hsp70, the entire TRIM5α structure is necessary to induce the morphological change of cells. When the ATPase domain of Hsp70 was mutated, the mutated Hsp70 could not counteract the morphological change induced by TRIM5α, indicating that the catalytic activity of Hsp70 protein is important for this function. Co-expression of Hsp70 elevated the levels of TRIM5α in the detergent-soluble fraction with a concomitant decrease in the detergent-insoluble fraction. Together these results suggest that Hsp70 plays critical roles in the cellular management against the TRIM5α-induced cellular insults.     

恒河猴TRIM5α的组织分布及不同刺激促进PBMC中TRIM5α转录水平的上调

TRIM5α(tripartite motif protein 5-alpha)蛋白是恒河猴体内一种非常重要的限制因子,能抑制人免疫缺陷病毒(HIV-1, human immunodeficiency virus type 1)、马感染性贫血病毒(EIAV, equine infectious anemia virus)和猫免疫缺陷病毒 (FIV, feline immunodeficiencyvirus)等逆转录病毒的复制。恒河猴TRIM5α的组织分布以及在受到外界刺激时TRIM5α mRNA表达量的变化研究还未见报道。本研究从中国恒河猴的各组织中提取总RNA,以β-actin基因作为内参照,通过半定量RT-PCR检测各组织中TRIM5α mRNA的表达。选择HIV-GFP-VSVG假病毒感染外周血单核细胞（peripheral blood mononuclear cell,PBMC）,非特异性刺激剂——佛波脂(Phorbol myfismte acetate,PMA)+离子霉素(ionomycin,Ion)及CD28抗体+CD49d抗体分别共刺激恒河猴PBMC,研究不同刺激对恒河猴TRIM5α mRNA表达水平的影响。结果表明：TRIM5α mRNA表达于所研究的恒河猴21种组织中,免疫系统和泌尿生殖系统组织中表达量最高,而神经系统组织,如大脑、脊髓中表达较少,其他组织中未见明显的表达差异;HIV-GFP-VSVG感染和用PMA+Ion、CD28抗体+CD49d抗体分别共刺激PBMC能促进 PBMC中TRIM5α mRNA的转录水平的上调。     

Metabolism of 17α-methyl-5α-dihydrotestosterone in the rabbit

17α-Methyl-5α-dihydrotestosterone and the reduced metabolites, 17α-methyl-5α-androstane-3α, 17β-diol and -3β, 17β-diol together with two hydroxylated metabolites, 17α-methyl-5α-androstane-3β, 15α, 17β-triol and 17α-methyl-5α-androstane-3α, 6α, 17β-triol were isolated and identified in the urine of rabbits orally dosed with 17α-methyl-5α-dihydrotestosterone. Formation of the C-6 hydroxylated derivative demonstrates that the 4,6-enolization of a 4-en-3-one is not a necessary requirement for hydroxylation at C-6 of the androstane nucleus in the rabbit. No evidence was obtained for the presence of 17α-methyl/17β-hydroxyl epimerization.     

利用TALEN技术建立恒河猴TRIM5α基因突变细胞株

利用TALEN技术建立恒河猴TRIM5α基因突变细胞株,为进一步研究TRIM5α基因的功能奠定基础。构建针对TRIM5α打靶基因的TALEN,通过点突变的方法获得包含TRIM5α第7个外显子中打靶位点1 211-1 224的基因序列并构建点突变donor载体。将打靶TRIM5α基因的TALEN质粒和donor质粒电转入恒河猴肾细胞(LLC-MK2)中,无限稀释法获得单克隆细胞系,通过抽提基因组DNA,再利用PCR技术扩增目标序列并测序筛选出TRIM5α碱基缺失(1 215-1 216)和点突变(1 213-1 215,1 217)的细胞系。通过共转TALEN质粒和点突变的donor质粒筛选获得了TRIM5α基因敲除和TRIM5α基因点突变的LLC-MK2细胞系。     

人天然免疫基因TRIM5α的序列及进化分析

目的：克隆人TRIM5α基因,对其编码序列进行分析,并进行分子进化研究。方法：以HeLa细胞cDNA为模板,用RT-PCR方法克隆人TRIM5α基因,与人基因组序列对比分析其结构;用BioEdit、Genedoc和MEGA4.1软件进行蛋白序列联配和进化分析。结果：扩增了长1482bp的人TRIM5α基因片段,序列分析表明其覆盖了完整编码框,编码由493个氨基酸残基组成的人TRIM5α蛋白;人TRIM5α蛋白与黑猩猩、大猩猩、猩猩、猕猴TRIM5α蛋白的相似度分别为98.2%、96.8%、93.7%和87.6%。结论：克隆了人TRIM5α基因,为进一步研究该基因的功能奠定了基础。     

Suppressor of Cytokine Signaling 1 Counteracts Rhesus Macaque TRIM5α-Induced Inhibition of Human Immunodeficiency Virus Type-1 Production

Old world monkey TRIM5α is a host factor that restricts human immunodeficiency virus type-1 (HIV-1) infection. Previously, we reported that rhesus macaque TRIM5α (RhTRIM5α) restricts HIV-1 production by inducing degradation of precursor Gag. Since suppressor of cytokine signaling 1 (SOCS1) is known to enhance HIV-1 production by rescuing Gag from lysosomal degradation, we examined if SOCS1 is involved in RhTRIM5α-mediated late restriction. Over-expression of SOCS1 restored HIV-1 production in the presence of RhTRIM5α to a level comparable to that in the absence of RhTRIM5α in terms of titer and viral protein expression. Co-immunoprecipitation studies revealed that SOCS1 physically interacted with RhTRIM5α. Over-expression of SOCS1 affected RhTRIM5α expression in a dose-dependent manner, which was not reversed by proteasome inhibitors. In addition, SOCS1 and RhTRIM5α were detected in virus-like particles. These results suggest that SOCS1 alleviates RhTRIM5α-mediated regulation in the late phase of HIV-1 life cycle probably due to the destabilization of RhTRIM5α.     

Inhibitory effect of human TRIM5α on HIV-1 production

Tripartite motif-containing 5 isoform-α (TRIM5α), a host restriction factor, blocks infection of some retroviruses at a post-entry, pre-integration stage in a species-specific manner. A recent report by Sakuma et al. describes a second antiretroviral activity of rhesus macaque TRIM5α, which blocks HIV-1 production through rapid degradation of HIV-1 Gag polyproteins. Here, we find that human TRIM5α limits HIV-1 production. Transient expression of TRIM5α decreased HIV-1 production, whereas knockdown of TRIM5α in human cells increased virion release. A single amino acid substitution (R437C) in the SPRY domain diminished the restriction effect. Moderate levels of human wild-type TRIM5α and a little amount of R437C mutant were incorporated into HIV-1 virions. The R437C mutant also lost restriction activity against N-tropic murine leukemia virus infection. However, the corresponding R to C mutation in rhesus macaque TRIM5α had no effect on the restriction ability. Our findings suggest human TRIM5α is an intrinsic immunity factor against HIV-1 infection. The importance of arginine at 437 aa in SPRY domain for the late restriction is species-specific.