Patterson C E, Shenk T
Howard Hughes Medical Institute, Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544-1014, USA.
J Virol. 1999 Sep;73(9):7126-31. doi: 10.1128/JVI.73.9.7126-7131.1999.
Consistent with earlier analyses of human cytomegalovirus UL36 mRNA, we find that the UL36 protein is present throughout infection. In fact, it is delivered to the infected cell as a constituent of the virion. Curiously, much less UL36 protein accumulated in cells infected with the AD169 strain of human cytomegalovirus than in cells infected with the Towne or Toledo strain, and localization of the protein in cells infected with AD169 is strikingly different from that in cell infected with the Towne or Toledo strain. The variation in steady-state level of the proteins results from different stabilities of the proteins. The UL36 proteins from the three viral strains differ by several amino acid substitutions. However, this variability is not responsible for the different half-lives because the AD169 and Towne proteins, which exhibit very different half-lives within infected cells, exhibit the same half-life when introduced into uninfected cells by transfection with expression plasmids. We demonstrate that the UL36 protein is nonessential for growth in cultured cells, and we propose that the ability of the virus to replicate in the absence of UL36 function likely explains the striking strain-specific variation in the half-life and intracellular localization of the protein.
与早期对人巨细胞病毒UL36 mRNA的分析一致，我们发现UL36蛋白在整个感染过程中都存在。事实上，它作为病毒粒子的一个组成部分被递送至被感染细胞。奇怪的是，在感染人巨细胞病毒AD169株的细胞中积累的UL36蛋白比感染汤氏或托莱多株的细胞中少得多，并且该蛋白在感染AD169的细胞中的定位与感染汤氏或托莱多株的细胞中的定位明显不同。蛋白质稳态水平的差异是由蛋白质不同的稳定性导致的。来自三种病毒株的UL36蛋白存在几个氨基酸替换的差异。然而，这种变异性并非导致不同半衰期的原因，因为AD169和汤氏蛋白在受感染细胞内表现出非常不同的半衰期，但通过用表达质粒转染引入未感染细胞时，它们表现出相同的半衰期。我们证明UL36蛋白对于在培养细胞中的生长并非必需，并且我们提出病毒在缺乏UL36功能的情况下进行复制的能力可能解释了该蛋白半衰期和细胞内定位中显著的毒株特异性差异。
