Project description:MLL undergoes multiple distinct chromosomal translocations to yield aggressive leukemia with dismal outcomes. Besides their well-established role in leukemogenesis, MLL fusions also possess latent tumor suppressive activity which can be exploited as effective cancer treatment strategies using pharmacological means such as proteasome inhibitors (PIs). Here, we show that wild-type MLL is indispensable for the latent tumor suppressive activity of MLL fusions. MLL dysfunction, shown as loss of the chromatin accessibility and subsequent degradation of MLL, compromises the latent tumor suppressive activity of MLL fusions and is instrumental for the acquired PI resistance. Mechanistically, MLL dysfunction is caused by chronic PI treatment-induced epigenetic reprogramming and can be specifically restored by histone deacetylase (HDAC) inhibitors.
Project description:MLL-fusions represent a large group of leukemia drivers, whose diversity originates from the vast molecular heterogeneity of C-terminal fusion partners of MLL protein. While studies of selected MLL-fusions have revealed critical molecular pathways, unifying mechanisms across all MLL-fusions remain poorly understood. We present the first comprehensive survey of protein-protein interactions of seven distantly related MLL-fusion proteins: MLL-AF1p, MLL-AF4, MLL-AF9, MLL-CBP, MLL-EEN, MLL-ENL and MLL-GAS7.
Project description:MLL fusions are leukemogenic transcription factors that enhance transcriptional elongation through modification of chromatin and RNAPolII. Global transcription rates and chromatin changes accompanying the transformation process were monitored by nascent-RNA-seq and ChIP-seq identifying 165 targets separated into two distinct clades. This accession contains ChIP Seq experiments for MLLENL and a negative control. The RNA-seq data set could also be found in ArrayExpress under accession number E-MTAB-3591 ( https://www.ebi.ac.uk/arrayexpress/experiments/E-MTAB-3591/ ).
Project description:Treatment of cells carrying MLL-rearrangements with VTP-50469 (specific Menin-MLL1 inhibitor) displaces Menin from high molecular weight complexes and chromatin genome-wide. Since VTP-50469 block Menin interaction with MLL1 we tested using chip-seq if treatment with VTP-50469 also displaces MLL1 or MLL-fusions from chromatin. We found that the VTP-50469 treatment displaced MLL-fusions from only a subset of MLL-fusion binding sites. Since DOT1L is associated with MLL-AF9 we then tested if displacement of MLL1 also leads to loss of DOT1L association with chromatin on MLL-AF9 binding sites. We found that DOT1L binds to thousands of genes, treatment with VTP-50469 leads to genome wide loss of DOT1L binding including the same subset of MLL-fusion binding sites.
Project description:MLL fusions are leukemogenic transcription factors that enhance transcriptional elongation through modification of chromatin and RNAPolII. Global transcription rates and chromatin changes accompanying the transformation process were monitored by nascent-RNA-seq and ChIP-seq identifying 165 targets separated into two distinct clades. ChIP-seq data complementing this RNA-seq data set can be found in ArrayExpress under accession number E-MTAB-3593 (http://www.ebi.ac.uk/arrayexpress/experiments/E-MTAB-3593)
Project description:Basic helix-loop-helix (bHLH) proneural transcription factors (TFs) Ascl1 and Neurog2 are integral to the development of the nervous system. Here, we investigated the molecular mechanisms by which Ascl1 and Neurog2 control the acquisition of generic neuronal fate and impose neuronal subtype identity. Using direct neuronal programming of embryonic stem cells, we found that Ascl1 and Neurog2 regulate distinct targets by binding to largely different sets of sites. Their divergent binding pattern is not determined by the previous chromatin state but distinguished by specific E-box enrichments which reflect the DNA sequence preference of the bHLH domain. The divergent Ascl1 and Neurog2 binding patterns result in distinct chromatin accessibility and enhancer activity landscapes that shape the binding and activity of downstream TFs during neuronal specification. Our findings suggest that proneural factors contribute to neuronal diversity by differentially altering the chromatin landscapes that shape the binding of neuronally expressed TFs.
Project description:Basic helix-loop-helix (bHLH) proneural transcription factors (TFs) Ascl1 and Neurog2 are integral to the development of the nervous system. Here, we investigated the molecular mechanisms by which Ascl1 and Neurog2 control the acquisition of generic neuronal fate and impose neuronal subtype identity. Using direct neuronal programming of embryonic stem cells, we found that Ascl1 and Neurog2 regulate distinct targets by binding to largely different sets of sites. Their divergent binding pattern is not determined by the previous chromatin state but distinguished by specific E-box enrichments which reflect the DNA sequence preference of the bHLH domain. The divergent Ascl1 and Neurog2 binding patterns result in distinct chromatin accessibility and enhancer activity landscapes that shape the binding and activity of downstream TFs during neuronal specification. Our findings suggest that proneural factors contribute to neuronal diversity by differentially altering the chromatin landscapes that shape the binding of neuronally expressed TFs.
Project description:RNA-Seq of 1) human AML samples; 2) sorted, uncultured distinct population from human cord blood (CB); 3) short-term (ST) cultured sorted CB cells transduced with MLL-ENL, MLL-AF6 or untransduced; and 4) cultured (LT) sorted CB cells transformed with MLL-ENL or MLL-AF6. Cells from MLL-fusion AML patients are bulk. Several cords were used for the sorting (CB1, CB2, CB3, 135, 141...) and these represent biological replicates. Several samples were sequenced several times in different lanes and results were merged together for the analysis (rep1,rep2...). Samples were used to determine the different effect of MLL-fusions in different celltypes just after the transduction, and after a longer time period when cells were transformed. Sorted CB samples, uncultured as well as transformed by MLL-fusions, were used in machine learning approach to predict which of the patients originated from which cell-type of origin.
Project description:Mixed-lineage leukemia (MLL) represents a genetically distinct and aggressive subset of human acute leukemia carrying chromosomal translocations of the MLL gene. These translocations result in oncogenic fusions that mediate aberrant recruitment of transcription machinery to MLL target genes. The N-terminus of MLL and MLL-fusions form a complex with Lens Epithelium-Derived Growth Factor (LEDGF/p75; encoded by the Psip1 gene) and MENIN. This complex contributes to the association of MLL and MLL-fusion multiprotein complexes with chromatin. Several studies have shown that both MENIN and LEDGF/p75 are required for efficient MLL fusion-mediated transformation and for the expression of downstream MLL-regulated genes like HOXA9 and MEIS1. In light of the development of a therapeutic strategy targeting this complex, understanding the function of LEDGF/p75 in normal hematopoiesis is crucial. We generated a conditional Psip1 knockout mouse model in the hematopoietic compartment and examined the effects of LEDGF/p75 depletion in postnatal hematopoiesis and the initiation of MLL leukemogenesis. Psip1 knockout mice were viable but showed several defects in hematopoiesis, reduced colony-forming activity in vitro, decreased expression of Hox genes in hematopoietic stem cells and decreased MLL occupancy at MLL target genes. Finally, in vitro and in vivo experiments showed that LEDGF/p75 is dispensable for steady state hematopoiesis but essential for the initiation of MLL-mediated leukemia. These data corroborate the MLL-LEDGF/p75 interaction as novel target for the treatment of MLL-rearranged leukemia.
Project description:Basic helix-loop-helix (bHLH) proneural transcription factors (TFs) Ascl1 and Neurog2 are integral to the development of the nervous system. Here, we investigated the molecular mechanisms by which Ascl1 and Neurog2 control the acquisition of generic neuronal fate and impose neuronal subtype identity. Using direct neuronal programming of embryonic stem cells, we found that Ascl1 and Neurog2 regulate distinct targets by binding to largely different sets of sites. Their divergent binding pattern is not determined by the previous chromatin state but distinguished by specific E-box enrichments which reflect the DNA sequence preference of the bHLH domain. The divergent Ascl1 and Neurog2 binding patterns result in distinct chromatin accessibility and enhancer activity landscapes that shape the binding and activity of downstream TFs during neuronal specification. Our findings suggest that proneural factors contribute to neuronal diversity by differentially altering the chromatin landscapes that shape the binding of neuronally expressed TFs.