Smits P H, de Wit L, van der Eb A J, Zantema A
Laboratory for Molecular Carcinogenesis, Sylvius Laboratory, Leiden University, The Netherlands.
Oncogene. 1996 Apr 4;12(7):1529-35.
Adenovirus E1A proteins modulate the expression of a large variety of genes in transformed cells by either stimulating or repressing their promoters. For example, the E1A proteins inhibit the collagenase promoter, whereas they activate the c-jun promoter. Both effects are mediated through AP-1/ATF-binding sites. Repression of transcription of the collagenase gene requires the amino-terminus and conserved region 1 (CR1) of Ad5 E1A, two regions that are also crucial for interaction of E1A with the recently isolated transcriptional adaptor protein p300. We show here that overexpressed p300 can counteract the repressive effect of E1A on the collagenase promoter. Using the CREB-binding protein (CBP), which is highly homologous to p300, the same results were obtained. The domains in E1A required for binding to p300 are also essential for E1A-mediated cell transformation. We therefore tested the effect of p300 and CBP on the transforming potential of Ad5 E1 in baby rat kidney (BRK) cells. It was found that E1A-induced focus formation was strongly inhibited by overexpression of p300 or CBP. Moreover the BRK cell colonies, obtained after cotransfection with Ad5E1 and p300, could not be established. These results indicate that one of the mechanisms by which E1A modulates transcription and transforms cells is via transcriptional adaptors like p300 and CBP.
腺病毒E1A蛋白通过刺激或抑制启动子来调节转化细胞中多种基因的表达。例如，E1A蛋白抑制胶原酶启动子，而激活c-jun启动子。这两种效应均通过AP-1/ATF结合位点介导。胶原酶基因转录的抑制需要Ad5 E1A的氨基末端和保守区域1（CR1），这两个区域对于E1A与最近分离的转录衔接蛋白p300的相互作用也至关重要。我们在此表明，过表达的p300可以抵消E1A对胶原酶启动子的抑制作用。使用与p300高度同源的CREB结合蛋白（CBP），也得到了相同的结果。E1A与p300结合所需的结构域对于EIA介导的细胞转化也至关重要。因此，我们测试了p300和CBP对Ad5 E1在新生大鼠肾（BRK）细胞中转化潜能的影响。发现p300或CBP的过表达强烈抑制了E1A诱导的集落形成。此外，用Ad5E1和p300共转染后获得的BRK细胞集落无法形成。这些结果表明，E1A调节转录和转化细胞的机制之一是通过p300和CBP等转录衔接蛋白。
