Induction of the small heat shock protein alphaB-crystallin by genotoxic stress is mediated by p53 and p73.
The small heat shock protein alphaB-crystallin is a molecular chaperone that is induced by stress and protects cells by inhibiting protein aggregation and apoptosis. To identify novel transcriptional regulators of the alphaB-crystallin gene, we examined the alphaB-crystallin promoter for conserved transcription factor DNA-binding elements and identified a putative response element for the p53 tumor suppressor protein. Ectopic expression of wild-type p53 induced alphaB-crystallin mRNA and protein with delayed kinetics compared to p21. Additionally, the induction of alphaB-crystallin by genotoxic stress was inhibited by siRNAs targeting p53. Although the p53-dependent transactivation of an alphaB-crystallin promoter luciferase reporter required the putative p53RE, chromatin immunoprecipitation failed to detect p53 binding to the alphaB-crystallin promoter. These results suggested an indirect mechanism of transactivation involving p53 family members p63 or p73. DeltaNp73 was dramatically induced by p53 in a TAp73-dependent manner, and silencing p73 suppressed the transcriptional activation of alphaB-crystallin by p53. Moreover, ectopic expression of DeltaNp73alpha (but not other p73 isoforms) increased alphaB-crystallin mRNA levels in the absence of p53. Collectively, our results link the molecular chaperone alphaB-crystallin to the cellular genotoxic stress response via a novel mechanism of transcriptional regulation by p53 and p73.
Evans
Joseph R
JR
Cell Death Regulation Lab, Departments of Medicine and Cell and Molecular Biology, Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Lurie 4-113, 303 East Superior Street, Chicago, IL 60611, USA.
Bosman
Joshua D
JD
Brown-Endres
Lauren
L
Yehiely
Fruma
F
Cryns
Vincent L
VL
D001665:Binding Sites; D002295:Carcinoma, Transitional Cell / Q000473:pathology; D045744:Cell Line, Tumor / Q000378:metabolism; D004249:DNA Damage / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology*; D004317:Doxorubicin / Q000633:toxicity; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D017930:Genes, Reporter; D055551:HSP27 Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D016297:Mutagenesis, Site-Directed; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D009687:Nuclear Proteins / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D020033:Protein Isoforms / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D016415:Sequence Alignment; D015533:Transcriptional Activation; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000502:physiology*; D001749:Urinary Bladder Neoplasms / Q000473:pathology; D038203:alpha-Crystallin B Chain / Q000096:biosynthesis / Q000235:genetics*
C059215:CRYAB protein, human; D004268:DNA-Binding Proteins; D055551:HSP27 Heat-Shock Proteins; C442250:HSPB2 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; C495901:TP53 protein, human; C000606460:TP73 protein, human; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D038203:alpha-Crystallin B Chain; C000606369:delta Np73 protein, human; D004317:Doxorubicin