Adenovirus type 5 E1A immortalizes primary rat cells expressing wild-type p53

Adenovirus (Ad) E1A induces apoptosis in cells expressing wad-type p53, and stable transformation by Ad E1A requires the co-introduction of an anti-ap optotic gene such as Ad E1B 19K, Thus, cells immortalized by Ad E1A alone m ight have lost functional p53, In order to analyze the p53 in rat cells exp ressing Ad E1A, we established rat cell lines by transfecting primary rat e mbryo fibroblast (REF) and baby rat kidney (BRK) cells with cloned Ad5 E1A. By using a yeast functional assay, we analyzed p53 in six primary REF and three BRK cell lines immortalized by Ad5 E1A as well as five spontaneously immortalized rat cell lines (REF52, NRK, WFB, Rat-1 and 3Y1), The yeast fun ctional assay revealed that all of the spontaneously and Ad5 E1A-immortaliz ed rat cell lines except for 3Y1 expressed wild-type p53. All of the Ad5 E1 A-immortalized rat cell lines contained p53 detectable by immunoprecipitati on. Recombinant adenovirus expressing rat p53 cloned from a REF cell line i mmortalized by Ad5 E1A, as well as that expressing murine wild-type p53, in duced apoptosis in p53-null cells in collaboration with E1A, Thus, it is su ggested that the mutation of p53 appears to be not frequent in the spontane ous immortalization of primary rat cells, and that the functional loss of w ild-type p53 is not a prerequisite of E1A-mediated immortalization.