Lanford R E, Butel J S
Cell. 1984 Jul;37(3):801-13. doi: 10.1016/0092-8674(84)90415-x.
An SV40-adenovirus 7 hybrid virus, PARA(cT), has been described that is defective for the nuclear transport of SV40 large tumor antigen. An SV40(cT) mutant was constructed using SV40 early and late region DNA fragments derived from PARA(cT) and wild-type SV40 respectively. The SV40(cT)-3 construct is defective for viral replication, but can be propagated in COS-1 cells. T antigen induced by SV40(cT)-3 is localized in the cytoplasm of infected cells. The cT mutation also inhibits the transport of wild-type T antigen; COS-1 cells lose their constitutive expression of nuclear T antigen after infection with SV40(cT)-3. Sequence analysis revealed that the cT mutation results in the replacement of a positively charged lysine in wild-type T antigen with a neutral asparagine at amino acid number 128, demonstrating that the alteration of a single amino acid is sufficient to abolish nuclear transport. Implications of the cT mutation on possible mechanisms for the transport of proteins to the nucleus are discussed.
一种SV40 - 腺病毒7杂交病毒PARA(cT)已被描述，它在SV40大T抗原的核转运方面存在缺陷。使用分别来自PARA(cT)和野生型SV40的SV40早期和晚期区域DNA片段构建了一种SV40(cT)突变体。SV40(cT)-3构建体在病毒复制方面存在缺陷，但可在COS - 1细胞中增殖。由SV40(cT)-3诱导的T抗原定位于被感染细胞的细胞质中。cT突变也抑制野生型T抗原的转运；COS - 1细胞在被SV40(cT)-3感染后失去其核T抗原的组成型表达。序列分析表明，cT突变导致野生型T抗原中一个带正电荷的赖氨酸在第128位氨基酸处被中性天冬酰胺取代，这表明单个氨基酸的改变足以消除核转运。文中讨论了cT突变对蛋白质向细胞核转运可能机制的影响。
