Hruby D E, Ball L A
J Virol. 1981 Nov;40(2):456-64. doi: 10.1128/JVI.40.2.456-464.1981.
mRNA extracted from vaccinia virus-infected cells early after infection directs cell-free synthesis of enzymatically active viral thymidine kinase (Hruby and Ball, Virology, in press). We used this assay for a specific vaccinia virus mRNA to study the induction and repression of the viral thymidine kinase gene during infection of thymidine kinase-deficient L-cells. As observed previously by other workers, the synthesis of thymidine kinase occurred immediately after infection but was switched off after 4 h later. We observed similar kinetics of accumulation and shutoff under conditions where viral DNA synthesis and late gene expression were inhibited. Cell-free translation of mRNA from infected cells showed that the concentration of functional message for viral thymidine kinase reached a peak 3 to 4 h after infection and then decreased with a half-life of about 1 h. These kinetics indicated that significant levels of thymidine kinase mRNA persisted in cells which had stopped synthesizing the enzyme. Under conditions where late gene expression was inhibited, high concentrations of functional mRNA could be isolated from cells at late times after infection. On the basis of these results, we conclude that the repression of thymidine kinase expression is mediated at the translational level by one or more early or delayed early viral genes. Repression is accompanied by, but does not depend on, the inactivation or degradation of thymidine kinase mRNA, which is a late gene function.
感染后早期从牛痘病毒感染细胞中提取的mRNA可指导无细胞体系合成具有酶活性的病毒胸苷激酶（赫鲁比和鲍尔，《病毒学》，即将发表）。我们利用这种针对特定牛痘病毒mRNA的检测方法，研究了胸苷激酶缺陷型L细胞感染过程中病毒胸苷激酶基因的诱导和抑制情况。正如其他研究人员之前所观察到的，胸苷激酶的合成在感染后立即发生，但在4小时后停止。在病毒DNA合成和晚期基因表达受到抑制的条件下，我们观察到了类似的积累和关闭动力学。对感染细胞的mRNA进行无细胞翻译显示，病毒胸苷激酶功能性信息的浓度在感染后3至4小时达到峰值，然后以约1小时的半衰期下降。这些动力学表明，在已经停止合成该酶的细胞中，仍存在大量的胸苷激酶mRNA。在晚期基因表达受到抑制的条件下，在感染后的晚期可以从细胞中分离出高浓度的功能性mRNA。基于这些结果，我们得出结论，胸苷激酶表达的抑制是由一个或多个早期或延迟早期病毒基因在翻译水平介导的。抑制伴随着胸苷激酶mRNA的失活或降解，但并不依赖于此，胸苷激酶mRNA的失活或降解是一种晚期基因功能。
