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.
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.
Joseph R
JR
Evans
Joshua D
JD
Bosman
Lauren
L
Brown-Endres
Fruma
F
Yehiely
Vincent L
VL
Cryns
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