In a previous genomic analysis, using somatic methyltransferase (DNMT) knockout 
cells, we showed that hypomethylation decreased the expression of as many genes 
as were observed to increase, suggesting a previously unknown mechanism for 
epigenetic regulation. To address this idea, the expression of the BAG family 
genes was used as a model. These genes were used because their expression was 
decreased in DNMT1(-/-), DNMT3B(-/-), and double knockout cells and increased in 
DNMT1-overexpressing and DNMT3B-overexpressing cells. Chromatin 
immunoprecipitation analysis of the BAG-1 promoter in DNMT1-overexpressing or 
DNMT3B-overexpressing cells showed a permissive dimethyl-H3-K4/dimethyl-H3-K9 
chromatin status associated with DNA-binding of CTCFL/BORIS, as well as 
increased BAG-1 expression. In contrast, a nonpermissive 
dimethyl-H3-K4/dimethyl-H3-K9 chromatin status was associated with CTCF 
DNA-binding and decreased BAG-1 expression in the single and double DNMT 
knockout cells. BORIS short hairpin RNA knockdown decreased both promoter 
DNA-binding, as well as BAG-1 expression, and changed the 
dimethyl-H3-K4/dimethyl-H3-K9 ratio to that characteristic of a nonpermissive 
chromatin state. These results suggest that DNMT1 and DNMT3B regulate BAG-1 
expression via insulator protein DNA-binding and chromatin dynamics by 
regulating histone dimethylation.