Interactions between SV40 large-tumor antigen and the growth suppressor proteins pRB and p53.

The oncogenic property of simian virus 40 depends in large part on the function of the virus-coded T-antigen. Although the precise mechanism of how T functions during neoplastic transformation is not clear, some answers to this question may lie in our understanding the nature of the proteins found to complex with T. The cellular protein p53 is perhaps the most extensively studied protein in this regard. Recently, p53 was defined as a growth suppressor protein. At about this same time, T was found to complex with another cell growth suppressor protein, the product of the retinoblastoma susceptibility gene. It has since become apparent that complex formation between these proteins affects their individual growth-modulating activities. Quite often this alteration of activity correlates with an uncontrolled proliferative state of the cell. Thus, transformation by SV40 is thought to involve complex formation between the viral T oncoprotein and cellular growth suppressor proteins. This complex formation is believed to result in nullification of the growth suppressor protein properties, thus increasing the propensity of the cell toward uncontrolled growth, the hallmark of neoplastic transformation.