Holman P S, Gjoerup O V, Davin T, Schaffhausen B S
Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111.
J Virol. 1994 Feb;68(2):668-73. doi: 10.1128/JVI.68.2.668-673.1994.
Polyomavirus large T antigen has an N-terminal domain of approximately 260 amino acids which can immortalize primary cells but lacks sequences known to be required for DNA binding and replication. Treatment of full-length large T with either V8 protease or chymotrypsin yields an N-terminal fragment of 36 to 40 kDa and a C-terminal fragment of approximately 60 kDa. This finding suggests a division of the protein into two domains. Proteolysis experiments show that the N-terminal domain does not have strong physical association with the rest of the protein. It also does not self-associate. A construct expressing only the N-terminal 259 amino acids is sufficient for immortalization. The independently expressed N-terminal domain is multiply phosphorylated, although at a lower level than the same region in full-length large T. The 259-residue protein binds to both pRb and p107 with somewhat lower efficiency than the full-length protein.
多瘤病毒大T抗原具有一个约260个氨基酸的N端结构域，该结构域可使原代细胞永生化，但缺乏已知的DNA结合和复制所需序列。用V8蛋白酶或胰凝乳蛋白酶处理全长大T会产生一个36至40 kDa的N端片段和一个约60 kDa的C端片段。这一发现表明该蛋白质可分为两个结构域。蛋白水解实验表明，N端结构域与蛋白质的其余部分没有很强的物理关联。它也不会自我缔合。仅表达N端259个氨基酸的构建体就足以实现永生化。独立表达的N端结构域会发生多重磷酸化，尽管其水平低于全长大T中相同区域。这个由259个残基组成的蛋白质与pRb和p107结合的效率比全长蛋白质略低。
