Studies on p53 and its role in cell proliferation

Abstract

p53 is a highly conserved nucle6-phosphoprotein expressed at ~ow levels in a cell cycle newlinespecific manner. The ability of the genomic and eDNA clones of p53 to immortalize primary newlinecells, and transform cultured cells in cooperation with ras suggested that p53 was likely to be newlinean oncogene. However, recently, it has been shown to be a tumor suppressor involved in the newlineregulation of cell division and malignant transformation. newlineThe Simian Virus 40 (SV40) is a double stranded DNA tumor virus that can transform newlinea normal cell into a malignant cell. It was thought that one of the mechanisms by which SV40 newlinecan transform the cells is by altering the p53 levels. In SV 40 transformed cells, the level of newlinep53 is fifty fold higher and this is due to an increased stability of the protein conferred by newlineformation of a complex with the large T antigen coded by SV 40. newlineHowever, in 3Tl2 and 312 cells transfected with SV40, the interaction between p53 newlineand the T antigen was not detected. The main aim of this study was to determine the cause for newlinethe failure of interaction between p53 and the T antigen in SV40 transformed 3T12 and 312 cell newlinelines. The lack of interaction between the T antigen and p53 could possibly be due to changes newlinein either the T antigen or p53 or the cellular environment in which they interact. It has been newlineshown that the T antigen was not altered in these cell lines. The p53 specific monoclonal newlineantibody, PAb246, failed to recognize p53 in 3T12 and 312 cells suggesting that either a newlinemutation in p53 or a change in the post-translational modification could be responsible for this newlinelack of interaction. newlineIn order to determine whether there was any change in the primary structure of p53, newlinetwo eDNA libraries, one from each cell line, were constructed in A.gtlO and the clones newlinecontaining the p53 sequences were identified by screening with a p53 eDNA probe. The newlinecomplete nucleotide sequence ofp53 from 3T12 and 312 cell lines was determined from the newlinelargest eDNA that hybridized to the p53 probe.