PML and acute promyelocytic leukemia: Proteins of the MLL core complex have been shown to bind and promote H3K4 methylation at the HLA-DRA promoter [35], and intriguingly, interaction between MLL and PML (promyelocytic leukemia) has been shown to prolong the dimethylation state of H3K4 and maintain transcriptional memory by localization to PML nuclear bodies [36].