Chiba A, Suzutani T, Saijo M, Koyano S, Azuma M
Department of Microbiology, Asahikawa Medical College, Japan.
Acta Virol. 1998 Dec;42(6):401-7.
To analyze the difference in the degree of divergence between genes from identical herpesvirus species, we examined the nucleotide sequence of genes from the herpes simplex virus type 1 (HSV-1) strains VR-3 and 17 encoding thymidine kinase (TK), deoxyribonuclease (DNase), protein kinase (PK; UL13) and virion-associated host shutoff (vhs) protein (UL41). The frequency of nucleotide substitutions per 1 kb in TK gene was 2.5 to 4.3 times higher than those in the other three genes. To prove that the polymorphism of HSV-1 TK gene is common characteristic of herpesvirus TK genes, we compared the diversity of TK genes among eight HSV-1, six herpes simplex virus type 2 (HSV-2) and seven varicella-zoster virus (VZV) strains. The average frequency of nucleotide substitutions per 1 kb in the TK gene of HSV-1 strains was 4-fold higher than that in the TK gene of HSV-2 strains. The VZV TK gene was highly conserved and only two nucleotide changes were evident in VZV strains. However, the rate of nonsynonymous substitutions in total nucleotide substitutions was similar among the TK genes of the three viruses. This result indicated that the mutational rates differed, but there were no significant differences in selective pressure. We conclude that HSV-1 TK gene is highly diverged and analysis of variations in the gene is a useful approach for understanding the molecular evolution of HSV-1 in a short period.
为了分析来自同一疱疹病毒物种的基因之间的差异程度，我们检测了单纯疱疹病毒1型（HSV-1）毒株VR-3和17中编码胸苷激酶（TK）、脱氧核糖核酸酶（DNase）、蛋白激酶（PK；UL13）和病毒体相关宿主关闭（vhs）蛋白（UL41）的基因的核苷酸序列。TK基因中每1 kb核苷酸替换的频率比其他三个基因高2.5至4.3倍。为了证明HSV-1 TK基因的多态性是疱疹病毒TK基因的共同特征，我们比较了8株HSV-1、6株单纯疱疹病毒2型（HSV-2）和7株水痘-带状疱疹病毒（VZV）毒株中TK基因的多样性。HSV-1毒株TK基因中每1 kb核苷酸替换的平均频率比HSV-2毒株TK基因高4倍。VZV TK基因高度保守，在VZV毒株中仅发现两个明显的核苷酸变化。然而，三种病毒的TK基因在总核苷酸替换中的非同义替换率相似。这一结果表明突变率不同，但选择压力没有显著差异。我们得出结论，HSV-1 TK基因高度分化，对该基因变异的分析是在短时间内了解HSV-1分子进化的一种有用方法。
