FHL2 mediates p53-induced transcriptional activation through a direct association with HIPK2.
To understand the molecular mechanism underlying HIPK2 regulation of the transcriptional activation by p53, we sought to identify the protein that interacts with HIPK2. From our yeast two-hybrid screen, we found that four and a half LIM domains 2 (FHL2) could bind to the C-terminal half of HIPK2. Further assays in yeast mapped the minimal interaction domain to amino acids 812-907 in HIPK2. The interaction was confirmed using a GST pull-down assay in vitro, and an immunoprecipitation (IP) assay and fluorescence microscopy in vivo. FHL2 alone spread throughout both the cytoplasm and nucleus but was redistributed to dot-like structures in the nucleus when HIPK2 was coexpressed in HEK293 cells. When tethered to the Gal4-responsive promoter through the Gal4 DBD fusion, FHL2 showed autonomous transcriptional activity that was enhanced by wild-type HIPK2, but not by the kinase-defective mutant. In addition, FHL2 increased the p53-dependent transcriptional activation and had an additive effect on the activation when coexpressed with HIPK2, which was again not observed with the kinase-defective mutant of HIPK2. Finally, we found a ternary complex of p53, HIPK2, and FHL2 using IP, and their recruitment to the p53-responsive p21Waf1 promoter in chromatin IP assays. Overall, our findings indicate that FHL2 can also regulate p53 via a direct association with HIPK2.
Lee
Sang-Wang
SW
Department of Bioscience and Biotechnology/Institute of Bioscience, Sejong University, Seoul, Republic of Korea.
Kim
Eun-Joo
EJ
Um
Soo-Jong
SJ
D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D006367:HeLa Cells; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D060850:LIM-Homeodomain Proteins; D009124:Muscle Proteins / Q000378:metabolism*; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D002352:Carrier Proteins; C105987:FHL2 protein, human; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D009124:Muscle Proteins; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; C115114:HIPK2 protein, human; D017346:Protein Serine-Threonine Kinases