Interactions of SV40 large T antigen and other viral proteins with retinoblastoma tumour suppressor

Simian virus 40 large T antigen, human papilloma virus E7 and adenovirus E1A are all potent oncoproteins that can induce several types of tumours. One of the major functions of these oncoproteins is to interact with the retinoblastoma tumour suppressor protein, Rb, a master switch of the mammalian cell cycle, and to inactivate its function. Rb promotes cell-cycle arrest by recruiting and regulating proteins involved in the transcription of cell proliferation genes. The binding of viral oncoproteins to Rb disrupts the Rb-E2F complex, a central component in the Rb-mediated cell-cycle network. The crystal structures of Rb pocket-viral oncoprotein complexes indicate that the viral proteins recognise a highly conserved region in the Rb pocket through a common motif, LxCxE, and through other unique regions within each viral protein. Although the mechanism of Rb inactivation by viral proteins is not fully understood, information at the atomic level about the interactions between the Rb pocket and viral proteins is providing some insights into how viral proteins dissociate E2F from Rb and thus how they deregulate the cell cycle.