Cell-type- and promoter-dependent ts phenotype of p53 Val135.
The p53 mutant Val135 is widely considered to have a wild-type (wt) phenotype at 32.5 degrees C, but not at 37 degrees C. The ability of wt murine p53 and its Val135 mutant to modulate transcription from the muscle-specific creatine kinase promoter (-3.3 kb pMCK), from a reporter construct containing two copies of the p53-binding DNA element from within MCK (p50-2), and from the interleukin-6 (IL-6) promoter (pIC225) was evaluated in transient transfection experiments in CV1 and HeLa cells. In CV1 cells, wt p53 was confirmed to activate the pMCK and p50-2 reporters, but to repress the IL-6 promoter. However, although in these cells p53 Val135 had the expected wt-like phenotype with respect to activation of the p50-2 reporter at 32.5 degrees C (32.5 degrees C > 37 degrees C), this mutant had little effect on expression from pMCK at either temperature, and activated rather than repressed the IL-6 promoter at 32.5 degrees C. In HeLa cells, although wt p53 activated p50-2 but repressed the MCK and IL-6 promoters, p53 Val135 activated all three reporters. Unexpectedly, in these cells the upregulation of p50-2 and pIC225 was basically temperature-independent, and that of pMCK was inversely ts (37 degrees C > 32.5 degrees C). The novel ts properties of p53 Val135 show that this mutant is not always wt-like at 32.5 degrees C but exhibits strong cell-type and promoter-dependent differences in its ts phenotype for transcriptional modulation.
Sehgal
P B
PB
Department of Microbiology and Immunology, New York Medical College, Valhalla 10595.
Margulies
L
L
D000818:Animals; D015500:Chloramphenicol O-Acetyltransferase / Q000032:analysis / Q000235:genetics; D003402:Creatine Kinase / Q000032:analysis / Q000235:genetics; D004247:DNA / Q000235:genetics; D016158:Genes, p53 / Q000235:genetics* / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics; D051379:Mice; D009132:Muscles / Q000201:enzymology; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D011401:Promoter Regions, Genetic / Q000235:genetics*; D013696:Temperature; D014158:Transcription, Genetic / Q000235:genetics; D014162:Transfection; D015854:Up-Regulation; D014633:Valine / Q000032:analysis*
D015850:Interleukin-6; D004247:DNA; D015500:Chloramphenicol O-Acetyltransferase; D003402:Creatine Kinase; D014633:Valine