A putative protein inhibitor of activated STAT (PIASy) interacts with p53 and inhibits p53-mediated transactivation but not apoptosis.
The p53 protein has recently been reported to be capable of mediating apoptosis through a pathway that is not dependent on its transactivation function. We report here that the PIASy member of the protein inhibitor of activated STAT family inhibited p53's transactivation function without compromising its ability to induce apoptosis of the H1299 nonsmall cell lung carcinoma cell line. The p53 protein bound to PIASy in yeast two-hybrid assays and coprecipitated in complexes with p53 in immunoprecipitates from mammalian cells. PIASy inhibited the DNA-binding activity of p53 in nuclear extracts and blocked the ability of p53 to induce expression of two of its target genes, Bax and p21Waf1/Cip1, in H1299 cells. The block in p53-mediated induction of Bax and p21 was determined to be at the level of transactivation, since PIASy inhibited p53's ability to transactivate a p21/luciferase reporter construct. PIASy did not effect the incidence of apoptosis in H1299 cells upregulated for p53. PIASy appears to regulate p53-mediated functions and may direct p53 into a transactivation-independent mode of apoptosis.
Nelson
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Department of Pathology, Texas A&M University Health Science Center, College Station 77843-1114, USA.
Davis
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GE
Maxwell
S A
SA
D000818:Animals; D017209:Apoptosis; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002469:Cell Separation; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors*; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D008156:Luciferases / Q000378:metabolism; D008175:Lung Neoplasms / Q000473:pathology; D051379:Mice; D010957:Plasmids / Q000378:metabolism; D000075223:Poly-ADP-Ribose Binding Proteins; D011233:Precipitin Tests; D011485:Protein Binding; D050828:Protein Inhibitors of Activated STAT; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050794:STAT1 Transcription Factor; D015534:Trans-Activators / Q000037:antagonists & inhibitors*; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; C494827:Bax protein, mouse; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; C485891:PIAS4 protein, human; D000075223:Poly-ADP-Ribose Binding Proteins; D050828:Protein Inhibitors of Activated STAT; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; C494080:Stat1 protein, mouse; D015534:Trans-Activators; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D004247:DNA; D008156:Luciferases; D016283:Proto-Oncogene Proteins p21(ras)