Homeodomain interacting protein kinase 2 promotes apoptosis by downregulating the transcriptional corepressor CtBP.
Genetic knockout of the transcriptional corepressor CtBP in mouse embryo fibroblasts upregulates several genes involved in apoptosis. We predicted, therefore, that a propensity toward apoptosis might be regulated through changes in cellular CtBP. To identify pathways involved in this regulation, we screened a mouse embryo cDNA library with an E1A-CtBP complex and identified the homeodomain interacting protein kinase 2 (HIPK2), which had previously been linked to UV-directed apoptosis through its ability to phosphorylate p53. Expression of HIPK2 or exposure to UV irradiation reduced CtBP levels via a proteosome-mediated pathway. The UV effect was prevented by coexpression of kinase-inactive HIPK2 or reduction in HIPK2 levels via siRNA. Mutation of the residue phosphorylated by HIPK2 prevented UV- and HIPK2-directed CtBP clearance. Finally, reduction in CtBP levels, either by genetic knockout or siRNA, promoted apoptosis in p53-deficient cells. These findings provide a pathway for UV-induced apoptosis in cells lacking p53.
Vollum Institute, Oregon Health and Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97239, USA. zhangq@ohsu.edu
Qinghong
Q
Zhang
Yasuhiro
Y
Yoshimatsu
Jeffrey
J
Hildebrand
Steven M
SM
Frisch
Richard H
RH
Goodman
D000429:Alcohol Oxidoreductases; D019943:Amino Acid Substitution; D000818:Animals; D017209:Apoptosis / Q000235:genetics* / Q000528:radiation effects; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D034741:RNA, Small Interfering / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D012694:Serine; D000429:Alcohol Oxidoreductases; C096794:C-terminal binding protein; C115114:HIPK2 protein, human; C492003:Hipk2 protein, mouse; D017346:Protein Serine-Threonine Kinases