MDM2 DELETION DOES NOT ALTER GROWTH-CHARACTERISTICS OF P53-DEFICIENT EMBRYO FIBROBLASTS

The mdma gene encodes a protein that is necessary for the negative reg ulation of p53 function in vivo. Deletion of the mdm2 gene in mice res ults in early embryonic death while concomitant mdm2 and p53 deletion results in viable offspring. The viability of these mice prompted us t o ask if MDM2, had an important growth regulatory function independent of p53. We established mouse embryo fibroblasts null for both p53 and mdma and compared them with p53-null fibroblasts. The cells did not d iffer in their growth rates or their ability to bypass a G(1) arrest. Both cell lines formed colonies efficiently when plated at low density and showed a similar degree of genetic instability. Thus, the analysi s of several growth parameters indicated no difference between p53-nul l and p53/mdm2-null cell lines.