Different Regions of the HPV-E7 and Ad-E1A Viral Oncoproteins Bind Competitively but through Distinct Mechanisms to the CH1 Transactivation Domain of p300

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• 作者：Daniela Fera ; Ronen Marmorstein
• 刊名：Biochemistry
• 出版年：2012
• 出版时间：November 27, 2012
• 年：2012
• 卷：51
• 期：47
• 页码：9524-9534
• 全文大小：465K
• 年卷期：v.51,no.47(November 27, 2012)
• ISSN：1520-4995

文摘

p300 is a transcriptional coactivator that participates in many important processes in the cell, including proliferation, differentiation, and apoptosis. The viral oncoproteins, adenovirus (Ad) E1A and human papillomavirus (HPV) E7, have been implicated in binding to p300. The Ad-E1A鈥損300 interaction has been shown to result in the induction of cellular proliferation, epigenetic reprogramming, and cellular transformation and cancer. The HPV-E7鈥損300 interaction, on the other hand, is not well understood. p300 contains three zinc-binding domains, CH1鈥揅H3, and studies have shown that Ad-E1A can bind to the p300 CH1 and CH3 domains whereas E7 can bind to the CH1 domain and to a lesser extent to the CH2 and CH3 domains. Here we address how high-risk HPV16-E7 and Ad5-E1A, which have different structures, can both bind the p300 CH1 domain. Using pull-down, gel filtration, and analytical ultracentrifugation studies, we show that the N-terminus and CR1 domains of Ad5-E1A and the CR1 and CR2 domains of HPV16-E7 bind to the p300 CH1 domain competitively and with midnanomolar and low micromolar dissociation constants, respectively. We also show that Ad5-E1A can form a ternary complex with the p300 CH1 domain and the retinoblastoma pRb transcriptional repressor, whereas HPV16-E7 cannot. These studies suggest that the HPV16-E7 and Ad5-E1A viral oncoproteins bind to the same p300 CH1 domain to disrupt p300 function by distinct mechanisms.