Somasundaram K, El-Deiry W S
Department of Medicine and Genetics, University of Pennsylvania School of Medicine and Comprehensive Cancer Center, Philadelphia 19104, USA.
Oncogene. 1997 Mar 6;14(9):1047-57. doi: 10.1038/sj.onc.1201002.
Cellular transformation by the adenovirus E1A oncoprotein requires its p300/CBP- and Rb-binding domains. We mapped inhibition of p53-mediated transactivation to the p300/CBP-binding region of E1A. An E1A mutant incapable of physically interacting with Rb retained the capacity to inhibit transactivation by p53, whereas E1A mutants of the p300/CBP-interacting domain failed to inhibit p53. The inhibitory effect of the p300/CBP-binding region of E1A on p53 was demonstrated with p53-activated reporters and endogenous p53 targets such as p21(WAF1/CIP1) or MDM2. E1A lacking the capacity to interact with Rb, but capable of p300/CBP interaction, was competent in suppression of a DNA-damage activated p53-dependent cell cycle checkpoint. Exogenous CBP and p300 were able to individually relieve E1A's inhibitory effect on p53-mediated transcription. Mutants of E1A that are not capable of interacting with p300 or CBP were found to efficiently stabilize endogenous p53 but were not competent in repression of p21 expression thus dissociating these two effects of E1A. Our results suggest that the p300/CBP-binding domain of E1A inhibits a p53-dependent cellular response which normally inhibits DNA replication following Adenovirus infection.
腺病毒E1A癌蛋白介导的细胞转化需要其p300/CBP结合域和Rb结合域。我们将p53介导的反式激活抑制定位到E1A的p300/CBP结合区域。一个不能与Rb发生物理相互作用的E1A突变体保留了抑制p53反式激活的能力，而p300/CBP相互作用域的E1A突变体则无法抑制p53。用p53激活的报告基因以及内源性p53靶标如p21（WAF1/CIP1）或MDM2证实了E1A的p300/CBP结合区域对p53的抑制作用。缺乏与Rb相互作用能力但能够与p300/CBP相互作用的E1A能够抑制DNA损伤激活的p53依赖性细胞周期检查点。外源性CBP和p300能够分别解除E1A对p53介导转录的抑制作用。发现不能与p300或CBP相互作用的E1A突变体能够有效地稳定内源性p53，但不能抑制p21的表达，从而使E1A的这两种作用分离。我们的结果表明，E1A的p300/CBP结合域抑制了p53依赖性细胞反应，这种反应通常在腺病毒感染后抑制DNA复制。
