Cutaneous T-cell lymphomas (CTCLs) are a subset of T-cell malignancies presenting in the skin. The treatment options for CTCL, in particular in advanced stages, are limited. One of the emerging... Show moreCutaneous T-cell lymphomas (CTCLs) are a subset of T-cell malignancies presenting in the skin. The treatment options for CTCL, in particular in advanced stages, are limited. One of the emerging therapies for CTCL is treatment with histone deacetylase (HDAC) inhibitors. We recently discovered an evolutionarily conserved crosstalk between HDAC1, one of the targets of HDAC inhibitors, and the histone methyltransferase DOT1L. HDAC1 negatively regulates DOT1L activity in yeast, mouse thymocytes, and mouse thymic lymphoma. Here we studied the functional relationship between HDAC inhibitors and DOT1L in two human CTCL cell lines, specifically addressing the question whether the crosstalk between DOT1L and HDAC1 observed in mouse T cells plays a role in the therapeutic effect of clinically relevant broad-acting HDAC inhibitors in the treatment of human CTCL. We confirmed that human CTCL cell lines were sensitive to treatment with pan-HDAC inhibitors. In contrast, the cell lines were not sensitive to DOT1L inhibitors. Combining both types of inhibitors did neither enhance nor suppress the inhibitory effect of HDAC inhibitors on CTCL cells. Thus our in vitro studies suggest that the effect of commonly used pan-HDAC inhibitors in CTCL cells relies on downstream effects other than DOT1L misregulation. Show less
Kollenstart, L.; Horst, S.C. van der; Vreeken, K.; Janssen, G.M.C.; Martino, F.; Vlaming, H.; ... ; Attikum, H. van 2021
The collection of known posttranslational modifications (PTMs) has expanded rapidly with the identification of various non-acetyl histone lysine acylations, such as crotonylation, succinylation and... Show moreThe collection of known posttranslational modifications (PTMs) has expanded rapidly with the identification of various non-acetyl histone lysine acylations, such as crotonylation, succinylation and butyrylation, yet their regulation is still not fully understood. Through an unbiased chromatin immunoprecipitation (ChIP)-based approach called Epigenetics-IDentifier (Epi-ID), we aimed to identify regulators of crotonylation, succinylation and butyrylation in thousands of yeast mutants simultaneously. However, highly correlative results led us to further investigate the specificity of the pan-K-acyl antibodies used in our Epi-ID studies. This revealed cross-reactivity and lack of specificity of pan-K-acyl antibodies in various assays. Our findings suggest that the antibodies might recognize histone acetylation in vivo, in addition to histone acylation, due to the vast overabundance of acetylation compared to other acylation modifications in cells. Consequently, our Epi-ID screen mostly identified factors affecting histone acetylation, including known (e.g. GCN5, HDA1, and HDA2) and unanticipated (MET7, MTF1, CLB3, and RAD26) factors, expanding the repertoire of acetylation regulators. Antibody-independent follow-up experiments on the Gcn5-Ada2-Ada3 (ADA) complex revealed that, in addition to acetylation and crotonylation, ADA has the ability to butyrylate histones. Thus, our Epi-ID screens revealed limits of using pan-K-acyl antibodies in epigenetics research, expanded the repertoire of regulators of histone acetylation, and attributed butyrylation activity to the ADA complex. Show less
Kwesi-Maliepaard, E.M.; Aslam, M.A.; Alemdehy, M.F.; Brand, T. van den; McLean, C.; Vlaming, H.; ... ; Jacobs, H. 2020
Cytotoxic T cell differentiation is guided by epigenome adaptations, but how epigenetic mechanisms control lymphocyte development has not been well defined. Here we show that the histone... Show moreCytotoxic T cell differentiation is guided by epigenome adaptations, but how epigenetic mechanisms control lymphocyte development has not been well defined. Here we show that the histone methyltransferase DOT1L, which marks the nucleosome core on active genes, safeguards normal differentiation of CD8(+) T cells. T cell-specific ablation of DOT1L resulted in loss of naive CD8(+) T cells and premature differentiation toward a memory-like state, independent of antigen exposure and in a cell-intrinsic manner. Mechanistically, DOT1L controlled CD8(+) T cell differentiation by ensuring normal T cell receptor density and signaling. DOT1L also maintained epigenetic identity, in part by indirectly supporting the repression of developmentally regulated genes. Finally, deletion of DOT1L in T cells resulted in an impaired immune response. Through our study, DOT1L is emerging as a central player in physiology of CD8(+) T cells, acting as a barrier to prevent premature differentiation and controlling epigenetic integrity. Show less
Welsem, T. van; Korthout, T.; Ekkebus, R.; Morais, D.; Molenaar, T.M.; Harten, K. van; ... ; Leeuwen, F. van 2018
