Co-operation between the p53 protein tumor antigen and platelet-poor plasma in the induction of cellular DNA synthesis.

Plasmids containing DNA sequences coding for p53 were microinjected into quiescent Swiss 3T3 cells. Three constructs were used, carrying either the whole gene sequence, a full-length cDNA, or a hybrid between the gene and the cDNA. All of them stimulated DNA synthesis when cells were incubated with platelet-poor plasma (PPP) following injection. The p53 gene stimulated DNA synthesis to a lesser extent, also in the absence of PPP. Several negative results were obtained with different plasmids, including deletion mutants in the p53 coding region. However, a deletion mutant in which the p53 reading frame ended in the middle of the coding part of the p53 gene still stimulated DNA synthesis in co-operation with PPP. The stimulation of DNA synthesis induced by p53 cDNA was more synchronous and more limited than that induced by serum. The present data suggest that p53 may act as a competence factor in cell cycle progression.