Martin M E, Piette J, Yaniv M, Tang W J, Folk W R
Department of Microbiology, University of Texas, Austin 78712.
Proc Natl Acad Sci U S A. 1988 Aug;85(16):5839-43. doi: 10.1073/pnas.85.16.5839.
The polyomavirus enhancer is composed of multiple DNA sequence elements serving as binding sites for proteins present in mouse nuclear extracts that activate transcription and DNA replication. We have identified three such proteins and their binding sites and correlate them with enhancer function. Mutation of nucleotide (nt) 5140 in the enhancer alters the binding site (TGACTAA, nt 5139-5145) for polyomavirus enhancer A binding protein 1 (PEA1), a murine homolog of the human transcription factor activator protein 1 (AP1). This mutation simultaneously reduces polyomavirus transcription and DNA replication. Reversion of this mutation simultaneously restores binding of PEA1 and both DNA replication and transcription. Binding of a second protein, PEA2, adjacent to the PEA1 site at nt 5147-5155 is enhanced by PEA1 binding, suggesting that these proteins interact. A third protein, PEA3, binds to the sequence AGGAAG (nt 5133-5138) adjacent to the PEA1 binding site; integrity of this late-proximal PEA3 binding site or an additional early-proximal site (nt 5228-5233) is important for enhancer function. We correlate binding of PEA1 and PEA2 with the induction of a DNase I-hypersensitive site in polyomavirus minichromosomes isolated from mouse fibroblasts.
多瘤病毒增强子由多个DNA序列元件组成，这些元件作为小鼠核提取物中蛋白质的结合位点，可激活转录和DNA复制。我们已鉴定出三种这样的蛋白质及其结合位点，并将它们与增强子功能相关联。增强子中核苷酸（nt）5140的突变改变了多瘤病毒增强子A结合蛋白1（PEA1）的结合位点（TGACTAA，nt 5139 - 5145），PEA1是人类转录因子激活蛋白1（AP1）的小鼠同源物。此突变同时降低了多瘤病毒的转录和DNA复制。该突变的回复同时恢复了PEA1的结合以及DNA复制和转录。第二种蛋白质PEA2在nt 5147 - 5155处与PEA1位点相邻结合，PEA1的结合增强了PEA2的结合，表明这些蛋白质相互作用。第三种蛋白质PEA3与PEA1结合位点相邻的序列AGGAAG（nt 5133 - 5138）结合；这个晚期近端PEA3结合位点或另一个早期近端位点（nt 5228 - 5233）的完整性对增强子功能很重要。我们将PEA1和PEA2的结合与从小鼠成纤维细胞中分离出的多瘤病毒微型染色体中DNase I超敏位点的诱导相关联。
