Rapid and accurate remethylation of DNA in deficient hematopoietic cells with restoration of DNMT3A activity.

Here, we characterize the DNA methylation phenotypes of bone marrow cells from mice with hematopoietic deficiency of or (or both enzymes) or expressing the dominant-negative mutation [R882H in humans; the most common mutation found in acute myeloid leukemia (AML)]. Using these cells as substrates, we defined DNA remethylation after overexpressing wild-type (WT) DNMT3A1, DNMT3B1, DNMT3B3 (an inactive splice isoform of DNMT3B), or DNMT3L (a catalytically inactive "chaperone" for DNMT3A and DNMT3B in early embryogenesis). Overexpression of for 2 weeks reverses the hypomethylation phenotype of Dnmt3a-deficient cells or cells expressing the R878H mutation. Overexpression of DNMT3L (which is minimally expressed in AML cells) also corrects the hypomethylation phenotype of marrow, probably by augmenting the activity of WT DNMT3A encoded by the residual WT allele. reactivation may represent a previously unidentified approach for restoring DNMT3A activity in hematopoietic cells with reduced DNMT3A function.