H3K9 methyltransferase G9a negatively regulates UHRF1 transcription during leukemia cell differentiation.
Bottom Line: Here, we provide evidence that UHRF1 is transcriptionally downregulated by H3K9 HMTase G9a.Finally, we showed that G9a regulates UHRF1-mediated H3K23 ubiquitination and proper DNA replication maintenance.Therefore, we propose that H3K9 HMTase G9a is a specific epigenetic regulator of UHRF1.
Affiliation: Department of Life Science, College of Natural Sciences, Chung-Ang University, Seoul 156-756.Show MeSH
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Mentions: To investigate whether the level of UHRF1 expression changes during leukemia cell differentiation, we treated HL-60 with TPA and monitored UHRF1 expression patterns using real-time PCR and western analysis. Previously, we reported that G9a expression was upregulated after leukemia cell differentiation (35). Consistent with our hypothesis, UHRF1 expression was significantly downregulated after leukemic HL-60 cell line differentiation by TPA (Figure 3A). Additionally, expression of G9a was upregulated upon differentiation of the HL-60 cell line (Figure 3A). Leukemic oncogene protein LMO2 was also downregulated when HL-60 cells differentiated. This indicates transcriptional repression of UHRF1 upon leukemia cell differentiation. To examine the recruitment of G9a before and after leukemia cell differentiation, we performed ChIP assays and real-time PCR on the UHRF1 promoter before and after TPA treatment. G9a recruitment to the UHRF1 promoter increased after TPA treatment, and levels of H3K9-me2 and H3K27-me3 overlapped well with G9a, YY1, and HDAC1 recruitment (Figure 3B). Pol II and Acetyl-H3 were not recruited after TPA treatment, though their association with HDAC2 was unaffected (Figure 3B). Together, these results suggest that transcription of UHRF1 is downregulated by G9a during leukemia cell differentiation. Altogether, these ChIP and real-time PCR data support a transcriptional regulatory relationship between G9a and UHRF1.
Affiliation: Department of Life Science, College of Natural Sciences, Chung-Ang University, Seoul 156-756.