T‐antigen expression by polyoma mutants with modified RNA splicing.
T‐antigen expression by polyoma mutants with modified RNA splicing.
复制标题
多瘤突变体通过修饰 RNA 剪接表达 T 抗原。
作者：
S. Nilsson;G. Magnusson
构建了不能表达所有三种T抗原的多瘤病毒突变体。诱变作用于早期RNA成熟过程中使用的两个5 '剪接位点。突变体bc1051在大T抗原mRNA的剪接位点上有碱基变化，而突变体dl1061和dl1062在小T抗原mRNA和中T抗原mRNA的相应剪接位点上有缺失。该位点在突变体dl1061中被移除，并通过与突变体dl1062的上游序列融合而改变。病毒RNA分析表明，dl1061和dl1062只形成大的T抗原mRNA，而bc1051不产生这种RNA。然而，dl1062的生物学特性表明，它也产生mRNA，至少在低量下指导小T抗原相关多肽的合成。只有突变体bc1051能诱导大鼠细胞转化。在小鼠3T3细胞中，dl1062增殖有限，而bc1051和dl1061不能产生病毒。然而，dl1061的DNA合成率较低，可以通过与突变体bc1051共转染将其增加到正常水平。这一结果表明，多瘤小T抗原和中T抗原在感染过程的早期阶段或病毒DNA合成中具有先前未被认识到的功能。
Polyoma virus mutants were constructed that could not express all the three T‐antigens. The mutagenesis was directed to the two 5′ splice sites utilized in the maturation of early RNA. The mutant bc1051 had a base change at the splice site of large T‐antigen mRNA, and the mutants dl1061 and dl1062 had deletions at the corresponding splice point of small and middle T‐antigen mRNA. The site was removed in mutant dl1061 and altered by fusion to upstream sequences in mutant dl1062. Analysis of viral RNA showed that dl1061 and dl1062 formed only large T‐antigen mRNA, whereas bc1051 did not produce this RNA‐species. However, the biological properties of dl1062 suggested that it also produced mRNA directing the synthesis of a small T‐antigen‐related polypeptide, at least in low amounts. Only mutant bc1051 could induce transformation of rat cells. In mouse 3T3 cells dl1062 multiplied to a limited extent, while bc1051 and dl1061 failed to produce virus. However, dl1061 DNA was synthesized at a low rate which could be increased to normal levels by co‐transfection with mutant bc1051. This result suggests that polyoma small and middle T‐antigen have a previously unrecognized function in the early phase of the infection process, or in viral DNA‐synthesis.