Rapid and accurate remethylation of DNA in <i>Dnmt3a-</i>deficient hematopoietic cells with restoration of DNMT3A activity.

Abstract

Here, we characterize the DNA methylation phenotypes of bone marrow cells from mice with hematopoietic deficiency of <i>Dnmt3a</i> or <i>Dnmt3b</i> (or both enzymes) or expressing the dominant-negative <i>Dnmt3a</i>^R878H mutation [R882H in humans; the most common <i>DNMT3A</i> 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 <i>DNMT3A</i> 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 <i>Dnmt3a</i>^R878H/+ marrow, probably by augmenting the activity of WT DNMT3A encoded by the residual WT allele. <i>DNMT3L</i> reactivation may represent a previously unidentified approach for restoring DNMT3A activity in hematopoietic cells with reduced DNMT3A function.