A murine erythroleukemic cell line (1-2-3) which expresses only the temperature-sensitive mutant p53 gene (Ala-to-Val substitution at codon 135) was established. When these cells were cultured at 32 degrees C, the growth rate was reduced significantly and DNA fragmentation, a typical character of apoptosis, was observed. In this process, p53 migrated from cytoplasm to nucleus and protein complexes binding to the p53-responsive element were detected in nuclear extracts of the cells cultured at 32 degrees C by gel-shift assay and transactivation from the p53-responsive element was detected. The expression of the p21 (waf1/cip1/sdi1), cyclin G and gadd45 genes was increased (about 3- to 4-fold that at 37 degrees C), when the cells were cultured at 32 degrees C. However, no significant change was detected in expression of the mdm2, bax and fas genes. No change in the amount of Fas antigen was observed by flow cytometric analysis. Transcripts of the bcl-2 and fas1 gene were not detected in the cells either at 37 degrees C or 32 degrees C. These results suggest that other gene(s) than bax, fas, fas1 and bcl-2 may be important for induction of apoptosis of this erythroleukemic cell line by p53.

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