van Cleef Koen W R, Scaf Wendy M A, Maes Karen, Kaptein Suzanne J F, Beuken Erik, Beisser Patrick S, Stassen Frank R M, Grauls Gert E L M, Bruggeman Cathrien A, Vink Cornelis
Department of Medical Microbiology, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, PO Box 5800, 6202 AZ Maastricht, The Netherlands.
J Gen Virol. 2004 Jul;85(Pt 7):2001-2013. doi: 10.1099/vir.0.79864-0.
An intriguing feature of the rat cytomegalovirus (RCMV) genome is open reading frame (ORF) r127, which shows similarity to the rep genes of parvoviruses as well as the U94 genes of human herpesvirus type 6A (HHV-6A) and 6B (HHV-6B). Counterparts of these genes have not been found in other herpesviruses. Here, it is shown that the r127 gene is transcribed during the early and late phases of virus replication in vitro as an unspliced 1.1 kb transcript containing the complete r127 ORF. Transcripts of r127 were also detected in various organs of RCMV-infected rats at 1 week post-infection (p.i.), but only in the salivary gland at 4 months p.i. Using rabbit polyclonal antibodies raised against the r127-encoded protein (pr127), pr127 was found to be expressed as early as 12 h p.i. within the nuclei of RCMV-infected cells in vitro. Expression of pr127 was also observed within the nuclei of cells in various organs of RCMV-infected rats at 3 weeks p.i. Moreover, pr127 was demonstrated to bind single- as well as double-stranded DNA. Finally, an RCMV r127 deletion mutant (RCMVDeltar127) was generated, in which the r127 ORF was disrupted. This deletion mutant, however, was shown to replicate with a similar efficiency as wild-type RCMV (wt RCMV), both in vitro and in vivo. Taken together, it is concluded that the RCMV r127 gene encodes a nuclear protein with single- and double-stranded DNA-binding activity that is dispensable for virus replication, not only in vitro, but also during the acute phase of infection in vivo.
大鼠巨细胞病毒（RCMV）基因组的一个有趣特征是开放阅读框（ORF）r127，它与细小病毒的rep基因以及人类6A型疱疹病毒（HHV-6A）和6B型疱疹病毒（HHV-6B）的U94基因具有相似性。在其他疱疹病毒中尚未发现这些基因的对应物。在此研究中发现，r127基因在体外病毒复制的早期和晚期转录为一个未剪接的1.1 kb转录本，其中包含完整的r127开放阅读框。在感染后1周（p.i.），也在RCMV感染大鼠的各种器官中检测到r127的转录本，但在感染后4个月仅在唾液腺中检测到。使用针对r127编码蛋白（pr127）产生的兔多克隆抗体，发现pr127早在体外RCMV感染细胞的细胞核中感染后12小时就开始表达。在感染后3周，在RCMV感染大鼠的各种器官的细胞细胞核中也观察到pr127的表达。此外，已证明pr127可结合单链和双链DNA。最后，构建了一个RCMV r127缺失突变体（RCMVDeltar127），其中r127开放阅读框被破坏。然而，该缺失突变体在体外和体内的复制效率与野生型RCMV（wt RCMV）相似。综上所述，得出的结论是，RCMV r127基因编码一种具有单链和双链DNA结合活性的核蛋白，该蛋白对于病毒复制是可有可无的，不仅在体外，而且在体内感染的急性期也是如此。
