Characteristics of Merkel Cell Polyomavirus T antigen oncoproteins.

Abstract

Merkel cell polyomavirus (MCV) is the first polyomavirus that can cause human cancer, and was discovered in January of 2008 (Huichen Feng, 2008). Its large T antigen shares structural and sequential similarities with SV40 T antigen and functional similarities with Human Papillomavirus (HPV) E7 proteins. These viral proteins have tumor transforming ability by binding to the tumor suppressor protein Retinoblastoma (Rb). In HPV infected cells, E7 binds to Rb and disrupts the Rb-E2F complex. Accumulation of free E2F then induces p16 expression (Samir N. Khleif, et al. 1996). Our hypothesis was if MCV and SV40 T antigens use the same mechanism, we should be able to observe induced p16 expression in cells transfected with MCV and SV40 T antigen plasmids. The p16 expression in LNCap cells transfected with SV40 and MCV full-length and C-terminal truncated T antigen plasmids were detected by immunofluorescence and western blot. Increased p16 expression was only observed in MCV full-length T antigen but not in truncated MCV T antigen or SV40 T antigen transfected cells. The results might be associated with different effects of epigenetic modification by MCV and SV40 T antigens.