Misra V, Bratanich A C, Carpenter D, O'Hare P
Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
J Virol. 1994 Aug;68(8):4898-909. doi: 10.1128/JVI.68.8.4898-4909.1994.
In herpes simplex virus (HSV)-infected cells, the transcription of immediate-early (alpha) genes is regulated by a virion component, the alpha gene trans-inducing factor (alpha TIF). This protein forms a complex with cellular factors and TAATGARAT motifs present in one or more copies in the promoters of all alpha genes. We have characterized the bovine herpesvirus 1 (BHV-1) homolog of this protein. Like its HSV counterpart, the BHV alpha TIF was synthesized in the later stages of infection and could be demonstrated to be a component of purified virions. In transient expression assays, BHV alpha TIF was a strong transactivator and stimulated the activity of IE-1, the major BHV-1 alpha gene promoter, with an efficiency comparable to that of HSV alpha TIF. This stimulation was largely dependent on a TAATGAGCT sequence present in a single copy in IE-1, and BHV alpha TIF, in conjunction with cellular factors, formed a complex with oligonucleotides containing this sequence. Despite these similarities between the two alpha TIFs, our preliminary observations suggest that the proteins may activate transcription by different mechanisms. Although BHV alpha TIF strongly transactivated IE-1, it differed from its HSV counterpart in that the carboxyl terminus of BHV alpha TIF, when fused to the DNA-binding domain of GAL4, was a relatively poor stimulator of a promoter containing GAL4-binding sites. Also unlike HSV alpha TIF, removal of the carboxyl terminus of BHV alpha TIF reduced but did not eliminate the ability of the protein to transactivate IE-1. These results are discussed in view of the structural similarities and differences among the alpha TIFs of alphaherpes-viruses.
在单纯疱疹病毒（HSV）感染的细胞中，立即早期（α）基因的转录受病毒体成分α基因反式诱导因子（αTIF）调控。该蛋白与细胞因子以及所有α基因启动子中一个或多个拷贝存在的TAATGARAT基序形成复合物。我们已对该蛋白的牛疱疹病毒1型（BHV-1）同源物进行了表征。与HSV的对应物一样，BHV αTIF在感染后期合成，并且可证明是纯化病毒体的一个成分。在瞬时表达试验中，BHV αTIF是一种强反式激活因子，可刺激主要的BHV-1 α基因启动子IE-1的活性，其效率与HSV αTIF相当。这种刺激很大程度上依赖于IE-1中单个拷贝存在的TAATGAGCT序列，并且BHV αTIF与细胞因子一起，与含有该序列的寡核苷酸形成复合物。尽管这两种αTIF之间存在这些相似性，但我们的初步观察表明，这两种蛋白可能通过不同机制激活转录。虽然BHV αTIF强烈反式激活IE-1，但其与HSV对应物的不同之处在于，当BHV αTIF的羧基末端与GAL4的DNA结合结构域融合时，它对含有GAL4结合位点的启动子的刺激作用相对较弱。同样与HSV αTIF不同的是，去除BHV αTIF的羧基末端会降低但不会消除该蛋白反式激活IE-1的能力。鉴于α疱疹病毒αTIF之间的结构相似性和差异，对这些结果进行了讨论。
