Tan X, Brunovskis P, Velicer L F
Department of Microbiology, Michigan State University, East Lansing, Michigan 48824-1101, USA.
J Virol. 2001 Mar;75(5):2067-75. doi: 10.1128/JVI.75.5.2067-2075.2001.
The various alphaherpesviruses, including Marek's disease virus (MDV), have both common and unique features of gene content and expression. The entire MDV U(s) region has been sequenced in our laboratory (P. Brunovskis and L. F. Velicar, Virology 206:324-338, 1995). Genes encoding the MDV glycoprotein D (gD), glycoprotein I (gI), and glycoprotein E (gE) homologs have been found in this region, although no gG homolog was found. In this work, transcription of the tandem MDV gD, gI, and gE genes was studied and found to have both unique characteristics and also features in common with other alphaherpesviruses. MDV gD could not be immunoprecipitated from MDV GA-infected duck embryo fibroblast cells by antisera reactive to its TrpE fusion proteins, while gI and gE could be. When the gD gene was subjected to in vitro-coupled transcription-translation, the precursor polypeptide was produced and could be immunoprecipitated by anti-gD. Northern blot, reverse transcriptase PCR, and RNase protection analyses have shown that (i) no mRNA initiating directly from the gD gene could be detected; (ii) a large but low-abundance 7.5-kb transcript spanning five genes, including the one encoding gD, was seen on longer exposure; and (iii) transcription of the gI and gE genes formed an abundant bicistronic 3.5-kb mRNA, as well as an abundant 2.0-kb gE-specific mRNA. Therefore, the MDV gD gene expression is down-regulated at the transcription level in MDV-infected cell culture, which may be related to the cell-associated nature of MDV in fibroblast cells. Compared to the highly gD-dependent herpes simplex virus and the other extreme of the varicella-zoster virus which lacks the gD gene, MDV is an intermediate type of alphaherpesvirus.
包括马立克氏病病毒(MDV)在内的各种甲型疱疹病毒在基因含量和表达方面既有共同特征,也有独特特征。我们实验室已对整个MDV U(s)区域进行了测序(P. Brunovskis和L. F. Velicar,《病毒学》206:324 - 338,1995年)。在该区域发现了编码MDV糖蛋白D(gD)、糖蛋白I(gI)和糖蛋白E(gE)同源物的基因,不过未发现gG同源物。在这项研究中,对串联的MDV gD、gI和gE基因的转录进行了研究,发现其既有独特特征,也有与其他甲型疱疹病毒相同的特征。用针对其TrpE融合蛋白的抗血清无法从感染MDV GA的鸭胚成纤维细胞中免疫沉淀出MDV gD,而gI和gE则可以。当gD基因进行体外偶联转录 - 翻译时,会产生前体多肽,并且可以被抗gD免疫沉淀。Northern印迹、逆转录酶PCR和核糖核酸酶保护分析表明:(i)未检测到直接从gD基因起始的mRNA;(ii)在长时间曝光时,可看到一个大的但低丰度的7.5 kb转录本,其跨越五个基因,包括编码gD的基因;(iii)gI和gE基因的转录形成了一个丰富的双顺反子3.5 kb mRNA,以及一个丰富的2.0 kb gE特异性mRNA。因此,在MDV感染的细胞培养物中,MDV gD基因表达在转录水平上受到下调,这可能与MDV在成纤维细胞中的细胞相关性质有关。与高度依赖gD的单纯疱疹病毒以及缺乏gD基因的水痘 - 带状疱疹病毒的另一端相比,MDV是甲型疱疹病毒的中间类型。