A TRANSCRIPT EXHIBITING HOMOLOGY TO ENDOGENOUS RAT RETROVIRAL-LIKE ELEMENTS IS REGULATED BY P53

Rat embryo fibroblasts transformed with HPV-16 E7 and the Ha-ras oncog ene (ER clones) fall into two distinct groups based on their endogenou s p53 status, wild-type or mutant, We have taken advantage of such clo nes in order to study the p53 target genes by the differential display method of RNA fingerprinting, We have identified a cDNA clone, clone 16, that recognises a large transcript on Northern blots. The clone 16 transcript is overexpressed in ER cell lines that express wild-type p 53 compared with ER cell lines that express mutant p53. Similar to the waf1/p21 gene, which is transcriptionally activated in cells treated with ionizing radiation in a p53-dependent manner, the clone transcrip t was also induced in response to irradiation, The sequence of clone 1 6 exhibits a high homology to two members of RAL retroviral-like eleme nts.