bcl-2 inhibits wild-type p53-triggered apoptosis but not G1 cell cycle arrest and transactivation of WAF1 and bax.
We have earlier shown that wild-type (wt) p53 expressed from a temperature-sensitive construct (ts p53) triggers apoptosis in the v-myc retrovirus-induced, p53-negative T-cell lymphoma line J3D (Y. Wang et al., Cell Growth & Differ., 4: 467-473, 1993). We also found that constitutive bcl-2 expression inhibits wt p53-triggered apoptosis in these cells (Y. Wang et al., Oncogene, 8: 3427-3431, 1993). Here we demonstrate that more than 90% of the ts p53-transfected J3D cells were arrested in G1 at 18 h after induction of wt p53 expression by temperature shift to 32 degrees C. At this time, at least 80% of the cells remained viable. After 30 h at 32 degrees C, around 50% of the cells had died by apoptosis, while most of the remaining cells were still alive in G1, indicating that p53-induced apoptosis occurred following G1 arrest. The G1 cell cycle arrest at 18 h after temperature shift to 32 degrees C was reversible, as shown by the fact that the cells readily resumed exponential growth following temperature shift back to 37 degrees C, although viability dropped from around 80 to 65%. Expression of both WAF1 and bax mRNA was induced by wt p53 in both the ts p53 and ts p53/bcl-2 transfected cells. The kinetics of G1 cell cycle arrest at 32 degrees C was similar in both the ts p53 and the ts p53/bcl-2 double transfectants.(ABSTRACT TRUNCATED AT 250 WORDS)
Wang
Y
Y
Microbiology and Tumor Biology Center, Karolinska Institute, Stockholm, Sweden.
Okan
I
I
Szekely
L
L
Klein
G
G
Wiman
K G
KG
D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D016193:G1 Phase / Q000235:genetics*; D016158:Genes, p53; D016399:Lymphoma, T-Cell / Q000235:genetics*; D051379:Mice; D011519:Proto-Oncogenes; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured