ABSTRACT
We report that H3K9 HMTase G9a activates transcription of the cell cycle regulatory gene, p21, in p53-null H1299 cells. Positive regulation of p21 by G9a is independent of its HMTase activity. We demonstrate that G9a upregulates p21 via interaction with PCAF, and provide evidence that the activating complex is recruited to the p21 promoter upon DNA damage-inducing agent etoposide treatment. Our study suggests that G9a decreases proliferation and cell viability by increasing the level of p21-mediated apoptosis. Our results suggest that G9a functions as a coactivator for p21 transcription, and directs cells to undergo apoptosis.
Subject(s)
Cyclin-Dependent Kinase Inhibitor p21/genetics , Histocompatibility Antigens/physiology , Histone-Lysine N-Methyltransferase/physiology , Transcriptional Activation , Apoptosis , Cell Line, Tumor , Cell Proliferation , Cyclin-Dependent Kinase Inhibitor p21/metabolism , DNA Damage , HEK293 Cells , Humans , Promoter Regions, Genetic , Protein Binding , RNA, Messenger/genetics , RNA, Messenger/metabolism , Up-Regulation , p300-CBP Transcription Factors/metabolismABSTRACT
Significant progress has been made in understanding the relationship between histone modifications and 'reader' molecules and their effects on transcriptional regulation. A previously identified INHAT complex subunit, SET/TAF-Iß, binds to histones and inhibits histone acetylation. To investigate the binding specificities of SET/TAF-Iß to various histone modifications, we employed modified histone tail peptide array analyses. SET/TAF-Iß strongly recognized PRC2-mediated H3K27me1/2/3; however, the bindings were completely disrupted by H3S28 phosphorylation. We have demonstrated that SET/TAF-Iß is sequentially recruited to the target gene promoter ATF3 after the PRC2 complex via H3K27me recognition and may offer additive effects in the repression of the target gene.
Subject(s)
Histone Chaperones/metabolism , Histones/metabolism , Transcription Factors/metabolism , Activating Transcription Factor 3/genetics , DNA-Binding Proteins , Epigenetic Repression , HeLa Cells , Histones/chemistry , Humans , Methylation , Models, Theoretical , Phosphorylation , Polycomb Repressive Complex 2/metabolism , Promoter Regions, Genetic , Protein Array Analysis , Protein Binding , Protein Processing, Post-Translational , Repressor Proteins/metabolism , Transcription, GeneticABSTRACT
Histone lysine methylation and demethylation are considered critical steps in transcriptional regulation. In this report, we performed chromatin immunoprecipitation with microarray technology (ChIP-chip) analysis to examine the genome-wide occupancy of H3K9-me2 during all-trans-retinoic acid (ATRA)-induced differentiation of HL-60 promyelocytic leukemia cells. Using this approach, we found that KDM3B, which contains a JmjC domain, was downregulated during differentiation through the recruitment of a corepressor complex. Furthermore, KDM3B displayed histone H3K9-me1/2 demethylase activity and induced leukemogenic oncogene lmo2 expression via a synergistic interaction with CBP. Here, we found that KDM3B repressed leukemia cell differentiation and was upregulated in blood cells from acute lymphoblastic leukemia (ALL)-type leukemia patients. The combined results of this study provide evidence that the H3K9-me1/2 demethylase KDM3B might play a role in leukemogenesis via activation of lmo2 through interdependent actions with the histone acetyltransferase (HAT) complex containing CBP.