Proper patterns of genome-wide DNA methylation, mediated by DNA methyltransferase DNMT1,-3A,-3B, are essential for embryonic development and genomic stability in mammalian cells. The de novo DNA methyltransferase DNMT3B is of particular interest because it is frequently overexpressed in tumor cells and is mutated in immunodeficiency, centromere instability and facial anomalies (ICF) syndrome. In order to gain a better insight into DNMT3B, we performed an yeast two-hybrid analysis using DNMT3B as a bait. Among various candidates, we confirmed that human polycomb protein hPc2 interact with DNMT3B in vivo and in vitro. Pulldown analysis with GST-DNMT3B demonstrated that DNMT3B physically interacts with hPc2, whereas DNMT3A or DNMT1 does not bind to hPC2. Analysis of DNMT3B and hPc2 deletion mutants showed that N-terminal of DNMT3b including PWWP and ATRX domain is required for the interaction with hPC2. Confocal microscopy showed that DNMT3B colocalized with hPc2 in nuclear. Regarding transcriptional regulation, we further found that DNMT3B enhanced transcriptional repression of hPc2. Finally, the result of cDNA microarray-based screening for target genes which are regulated by DNMT3b and hPC2 interaction will be presented in the meeting. Overall, these data support that mechanistic link between two essential epigenetic systems: polycomb group protein and DNA methylation machinery.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA