Fox D S, Schleiss M R
Division of Infectious Diseases, Children's Hospital Research Foundation, Cincinnati, Ohio 45229, USA.
Virus Genes. 1997;15(3):255-64. doi: 10.1023/a:1007988705909.
Guinea pig cytomegalovirus (GPCMV) displays a similar pathogenesis to human cytomegalovirus (HCMV), and the guinea pig has been used as a model system for testing anti-CMV therapies. However, not all agents active against HCMV share antiviral activity against GPCMV. For example, GPCMV appears resistant to the nucleoside analog, ganciclovir. The molecular basis for this discrepancy in antiviral susceptibility is unknown because to date there has been little analysis of the GPCMV genome. For HCMV, the antiviral effect of ganciclovir depends upon phosphorylation of the drug to its active form. This effect is mediated by the viral UL97 gene product. In order to begin to explore the molecular basis of the resistance of GPCMV to ganciclovir, experiments were undertaken to test whether the GPCMV genome encoded a homolog of the HCMV UL97 gene. Based on the prediction of co-linearity of UL97 homologs within the respective viral genomes, the EcoR I S and F fragments of the GPCMV genome were cloned and partially sequenced. A 1815 base pair open reading frame (ORF) capable of encoding a 604 amino acid (aa) protein was identified spanning portions of the EcoR I S and adjacent EcoR I F genome fragments. Computer-assisted matrix analyses revealed identity between this ORF and the HCMV UL97 gene. ORFs upstream of the GPCMV UL97 gene were identified which shared homology with the HCMV UL95 and 96 genes. Northern blot analyses identified a UL97-specific mRNA of 3.9 kb which was expressed at "early" times post-infection. RNA transcripts of 6.0 and 4.6 kb were identified which corresponded to the UL95 and UL96 homolog coding sequences, respectively. Comparison of the GPCMV UL97 sequence to that of other herpesvirus homologs as well as that of ganciclovir-resistant clinical isolates of HCMV identified nonconservative aa substitutions in two domains involved in catalysis and substrate recognition.
豚鼠巨细胞病毒（GPCMV）的发病机制与人类巨细胞病毒（HCMV）相似，豚鼠已被用作测试抗CMV疗法的模型系统。然而，并非所有对HCMV有活性的药物都对GPCMV具有抗病毒活性。例如，GPCMV似乎对核苷类似物更昔洛韦耐药。抗病毒敏感性存在这种差异的分子基础尚不清楚，因为迄今为止对GPCMV基因组的分析很少。对于HCMV，更昔洛韦的抗病毒作用取决于药物磷酸化为其活性形式。这种作用由病毒UL97基因产物介导。为了开始探索GPCMV对更昔洛韦耐药的分子基础，进行了实验以测试GPCMV基因组是否编码HCMV UL97基因的同源物。基于各自病毒基因组中UL97同源物共线性的预测，克隆了GPCMV基因组的EcoR I S和F片段并进行了部分测序。鉴定出一个1815个碱基对的开放阅读框（ORF），其能够编码一个604个氨基酸（aa）的蛋白质，跨越EcoR I S和相邻的EcoR I F基因组片段的部分。计算机辅助矩阵分析揭示了该ORF与HCMV UL97基因之间的同一性。鉴定出GPCMV UL97基因上游的ORF，其与HCMV UL95和96基因具有同源性。Northern印迹分析鉴定出一种3.9 kb的UL97特异性mRNA，其在感染后“早期”表达。鉴定出分别对应于UL95和UL96同源物编码序列的6.0和4.6 kb的RNA转录本。将GPCMV UL97序列与其他疱疹病毒同源物以及HCMV的更昔洛韦耐药临床分离株的序列进行比较，发现在参与催化和底物识别的两个结构域中存在非保守的氨基酸取代。
