Conserved crosstalk between histone deacetylation and H3K79 methylation generates DOT1L‐dose dependency in HDAC1‐deficient thymic lymphoma

Abstract

DOT 1L methylates histone H3K79 and is aberrantly regulated in MLL ‐rearranged leukemia. Inhibitors have been developed to target DOT 1L activity in leukemia, but cellular mechanisms that regulate DOT 1L are still poorly understood. We have identified the histone deacetylase Rpd3 as a negative regulator of budding yeast Dot1. At its target genes, the transcriptional repressor Rpd3 restricts H3K79 methylation, explaining the absence of H3K79me3 at a subset of genes in the yeast genome. Similar to the crosstalk in yeast, inactivation of the murine Rpd3 homolog HDAC 1 in thymocytes led to an increase in H3K79 methylation. Thymic lymphomas that arise upon genetic deletion of Hdac1 retained the increased H3K79 methylation and were sensitive to reduced DOT 1L dosage. Furthermore, cell lines derived from Hdac1 Δ/Δ thymic lymphomas were sensitive to a DOT 1L inhibitor, which induced apoptosis. In summary, we identified an evolutionarily conserved crosstalk between HDAC 1 and DOT 1L with impact in murine thymic lymphoma development.

The histone methyltransferase DOT1L prevents antigen-independent differentiation and safeguards epigenetic identity of CD8+T cells

“…The observed global loss of H3K79me2 in Lck-Cre +/-;Dot1L fl/fl mice, as confirmed by immunohistochemistry on fixed thymus tissue (Sup Fig. 1b), agreed with the notion that DOT1L is the sole methyltransferase for H3K79 11,25,28,29 .…”

“…DOT1L gained wide attention as a specific drug target in the treatment of MLL-rearranged leukemia, where MLL fusion proteins aberrantly recruit DOT1L to MLL target genes leading to their enhanced expression 22,23,24 . A similar dependency on DOT1L activity and sensitivity to DOT1L inhibitors was recently observed in thymic lymphoma 25 .…”

“…DOT1L gained wide attention as a specific drug target in the treatment of MLL-rearranged leukemia, where MLL fusion proteins aberrantly recruit DOT1L to MLL target genes leading to their enhanced expression [22][23][24] . A similar dependency on DOT1L activity and sensitivity to DOT1L inhibitors was recently observed in thymic lymphoma 25 . Interestingly, inhibition of DOT1L activity in human T cells attenuates graft-versus-host disease in adoptive cell transfer models 26 and it regulates CD4 + T cell differentiation 27 .…”

“…Given the essential role of DOT1L in embryonic development 28 , we determined the role of DOT1L in T cell development and differentiation by employing a conditional knock-out mouse model in which Dot1L is deleted in the T-cell lineage by combining floxed Dot1L with a Cre-recombinase under the control of the Lck promoter, which leads to deletion of exon 2 of Dot1L during early thymocyte development (Sup Fig. 1a) 25 . The observed global loss of H3K79me2 in Lck-Cre +/-;Dot1L fl/fl mice, as confirmed by immunohistochemistry on fixed thymus tissue (Sup Fig.…”

“…Lck-Cre;Dot1L fl/fl mice have been described elsewhere previously 25 and were based on the Dot1Ltm1a(KOMP)Wtsi line generated by the Wellcome Trust Sanger Institute (WTSI) and obtained from the KOMP Repository (www.komp.org) 96 Table 2). Of note, for OT-I tetramer stains the CD8 antibody clone 53-6.7 was used 98 .…”