Regulation of the cell cycle by viral oncoproteins.

Human papillomavirus (HPVs) adenovirus and simian virus 40 (SV40) are small DNA viruses which can show oncogenic activity. Although not otherwise related, all three have adopted very similar strategies to deregulate cell growth; each virus encoding oncoproteins which interact with the same cellular targets. Of particular interest are the interactions with the cell encoded pRB and p53 proteins, products of tumour suppressor genes. Somatic mutation results in the loss of the pRB and p53 function in many cancers and the contribution of the viruses to tumour development appears to reflect their ability to inactivate these cellular proteins. Both pRB and p53 negatively regulate progress through the cell cycle and the action of the viral proteins has highlighted the central importance of these tumour suppressor proteins in maintaining normal cell growth.