McIntyre M C, Frattini M G, Grossman S R, Laimins L A
Department of Biochemistry and Molecular Biology, University of Chicago, Illinois 60637.
J Virol. 1993 Jun;67(6):3142-50. doi: 10.1128/JVI.67.6.3142-3150.1993.
Human papillomavirus type 18 (HPV-18) E7 proteins bind zinc through Cys-X-X-Cys repeats located at the C terminus of the protein. In order to examine the role of these cysteine motifs in E7 function, we expressed the HPV-18 E7 protein in bacteria and found that purified E7 forms a dimer through interactions with zinc. Mutants with single mutations within the Cys-X-X-Cys motifs bound a reduced level of zinc in a zinc blot assay, while a double mutant lost all zinc-binding activity. When expressed in vivo, none of the mutants cooperated with an activated ras oncogene to transform primary rat embryo fibroblasts, but all mutants retained nearly wild-type Rb-binding activity. The results indicate that the cysteine motifs play an important role in transformation by HPV-18 E7 but do not contribute to Rb binding.
18型人乳头瘤病毒（HPV - 18）E7蛋白通过位于该蛋白C端的Cys - X - X - Cys重复序列结合锌。为了研究这些半胱氨酸基序在E7功能中的作用，我们在细菌中表达了HPV - 18 E7蛋白，发现纯化的E7通过与锌的相互作用形成二聚体。在Cys - X - X - Cys基序内具有单个突变的突变体在锌印迹试验中结合的锌水平降低，而双突变体则丧失了所有锌结合活性。当在体内表达时，没有一个突变体与活化的ras癌基因协同作用来转化原代大鼠胚胎成纤维细胞，但所有突变体都保留了几乎野生型的Rb结合活性。结果表明，半胱氨酸基序在HPV - 18 E7介导的转化中起重要作用，但对Rb结合没有贡献。
