The presence of a short form of p53 in chicken lymphoblastoid cell lines during apoptosis.

To examine the roles of a short form of p53 in the regulation of apoptosis in chicken lymphoblastoid tumor cell lines derived from Marek's disease (MD) and avian leukosis (AL), the expressions of the p53 proteins were analyzed in these cell lines in which apoptosis was chemically induced. In MSB1-O derived from MD, the expression of a 40 kDa protein of p53 was decreased and that of a 32 kDa protein, a short form of p53, was increased during apoptosis induced by actinomycin D. In 1104B1 derived from AL, the expressions of 42 and 32 kDa of p53 were increased during the apoptosis. The short form of p53 was undetectable in these cell lines when apoptosis was blocked by the pretreatment with endonuclease inhibitor, Zn2+, protease inhibitors, TPCK and TLCK, or caspase inhibitor, Z-VAD-FMK. In the transcriptional level, the expressions of bcl-2 and IAP were decreased in these cell lines during actinomycin D-induced apoptosis, but no change was detected in the expression level of p53. These results suggest that, in these chicken tumors, the short form of p53 could play a role in the initiation of apoptosis induced by the chemotherapeutic compound, and that the regulation of its expression may be important for the maintenance of transformation status.