Study on the functional interaction between HPV-E7 and cellular proteins = 파필로마바이러스 E7 단백질과 상호작용하는 세포내 단백질에 대한 연구

Abstract

The human papillomavirus (HPV) E7 oncoprotein can immortalize primary human cells and induce tumor formation. These properties of E7 depend on its ability to inhibit the activity of retinoblastoma protein (pRB), which in turn affects E2F function. E2F proteins control the expression of genes involved in differentiation, development, cell proliferation and apoptosis. Using genetic and biochemical approaches the present study shows that E7 binds to E2F1 in vivo and in vitro, and that both proteins co-localize in the nucleus. Importantly, the binding of the high-risk group HPV E7 to E2F1 is tighter than the binding of the low-risk group HPV E7 to E2F1. While E7 of the high-risk group HPVs activates E2F1-dependent transcription strongly in C33A or 293T cells, E7 of the low-risk group HPVs activates transcription only weakly. Using electrophoretic mobility shift assay we also showed that E7 binds to E2F1-DNA complexes. Furthermore, we show that these activities of E7 are independent of pRB by using E7 and E2F1 mutants that cannot bind to pRB. Taken together, these data suggest that E7 contributes to the deregulation of pRB-dependent E2F1 repression, and to the further activation of E2F1, independently of pRB. cAMP response element-binding protein-binding protein (CBP) and p300/CBP-associated factor (PCAF) are well-known general co-activators that contain multiple protein-protein interaction domains for association with various cellular and viral proteins. Using genetic and biochemical approaches the present study shows that E7 binds to CBP and PCAF in vivo and in vitro. We also identified the E7 binding domains in CBP in which include the cysteine/histidinerich domain3 (CH3). Transient transcription assays showed that HPV 16 E7 enhances the transcriptional activation function of CBP and PCAF. These results suggest that E7 can stimulate some cellular CBP or PCAF mediated promoters. In addition, we show that HPV E7 enhances the transcriptional activation function of C...