Project description:The goal of this study is to assess the role of ASH1 like histone lysine methyltransferase (ASH1L) in the biology of anaplastic thyroid cancer. CRISPR-Cas9 was used to create cell lines derived from BHT-101 anaplastic thyroid cancer cells with premature stop codons prior to the catalytic domain within both alleles of ASH1L. ChIP-seq for H3K36me2, the histone mark catalyzed by ASH1L, was performed on two KO cell lines, and compared to wild type BHT-101 cells.
Project description:The goal of this study is to assess the role of ASH1 like histone lysine methyltransferase (ASH1L) in the biology of anaplastic thyroid cancer. CRISPR-Cas9 was used to create 4 independent cell lines derived from BHT-101 anaplastic thyroid cancer cells with premature stop codons prior to the catalytic domain within both alleles of ASH1L. RNA-seq was performed on these 4 KO cell lines, and compared to 3 biological replicates of wild type BHT-101 cells.
Project description:Myoblast fusion (MF) is a complex process required for muscle formation. During development, post-natal muscle growth and adult muscle regeneration, myoblasts proliferate and fuse to generate multinucleated fibers. MF defects have been described in an increasing number of muscle diseases. Moreover, MF plays also a relevant role in the delivery of therapeutics to muscle fibers. Hence, the identification of novel MF activators bears strong therapeutic relevance. Despite the central role of MF, the mechanisms governing this process are incompletely understood, and no epigenetic regulator has ever been described. Ash1L is a histone methyltransferase responsible for H3K36me2 and a member of the Trithorax group of epigenetic activators. It is involved in several diseases, including FSHD muscular dystrophy, autism and cancer. Nevertheless, its physiological role in skeletal muscle is unknown. For the first time, we found that Ash1L expression is regulated during skeletal muscle development, positively correlated with that of key MF genes and reduced in Duchenne muscular dystrophy. During physiological muscle differentiation or muscle regeneration, Ash1L shows a peak of expression coincident with the activation of MF. Loss-of-function experiments support a selective and evolutionary conserved requirement for Ash1L in MF. Accordingly, Ash1L KO mice display small and underdeveloped skeletal muscles due to a MF defect. By combining RNA- and ChIP-sequencing, we identified direct Ash1L targets in muscle. Intriguingly, nearly all of them are known Polycomb target genes suggesting that Ash1L is required to counteract Polycomb repressive activity to allow activation of key myogenesis genes. In particular, we found that Ash1L drives MF by directly activating the expression of the key MF gene Cdon. Our results promote Ash1L as the first epigenetic regulator of MF and suggest that its activity could be targeted to improve cell therapy for muscle diseases.
Project description:To recognize DNA damage, nucleotide excision repair (NER) deploys a multipart mechanism by which the XPC sensor detects helical distortions followed by engagement of TFIIH for lesion verification. Accessory players ensure that this factor handover takes place on chromatin where DNA is wrapped around histones. We show that the histone methyltransferase ASH1L, once activated by MRG15, accelerates global-genome NER activity. Upon UV irradiation, ASH1L deposits H3K4me3 marks all over the genome (except in gene promoters), thus priming chromatin for relocations of XPC from native to damaged DNA. ASH1L further recruits the histone chaperone FACT to UV lesions. In the absence of ASH1L, MRG15 or FACT, XPC persists on damaged DNA without being able to deliver lesions to the TFIIH verifier. We conclude that ASH1L implements repair hotspots whose H3K4me3 and FACT occupancy confers an active promoter-like code and organization of histones that make DNA damage verifiable by the NER machinery.
Project description:The histone methyltransferases MLL and ASH1L are trithorax-group proteins that interact genetically through undefined molecular mechanisms to regulate developmental and hematopoietic gene expression. Here we show that the lysine 36-dimethyl mark of histone H3 (H3K36me2) written by ASH1L is preferentially bound in vivo by LEDGF, an MLL-associated protein that co-localizes with MLL, ASH1L and H3K36me2 on chromatin genome wide. Furthermore, ASH1L facilitates recruitment of LEDGF and wild type MLL proteins to chromatin at key leukemia target genes, and is a crucial regulator of MLL-dependent transcription and leukemic transformation. Conversely KDM2A, an H3K36me2 demethylase and Polycomb-group silencing protein, antagonizes MLL-associated leukemogenesis. Our studies illuminate the molecular mechanisms underlying epigenetic interactions wherein placement, interpretation and removal of H3K36me2 contribute to the regulation of gene expression and MLL leukemia, and suggest ASH1L as a target for therapeutic intervention. Investigation of multiple transcription factors and histone modification marks in MV4-11 human leukemia cells.
Project description:ASH1L and MLL1 are two histone methyltransferases that facilitate transcriptional activation during normal development. However, the roles of ASH1L and its enzymatic activity in the development of MLL-rearranged leukemias are not fully elucidated in Ash1L gene knockout animal models. In this study, we used an Ash1L conditional knockout mouse model to show that loss of ASH1L in hematopoietic progenitor cells impaired the initiation of MLL-AF9-induced leukemic transformation in vitro. Furthermore, genetic deletion of ASH1L in the MLL-AF9-transformed cells impaired the maintenance of leukemic cells in vitro and largely blocked the leukemia progression in vivo. Importantly, the loss of ASH1L function in the Ash1L-deleted cells could be rescued by wild-type but not the catalytic-dead mutant ASH1L, suggesting the enzymatic activity of ASH1L was required for its function in promoting MLL-AF9-induced leukemic transformation. At the molecular level, ASH1L enhanced the MLL-AF9 target gene expression by directly binding to the gene promoters and modifying the local histone H3K36me2 levels. Thus, our study revealed the critical functions of ASH1L in promoting the MLL-AF9-induced leukemogenesis, which provides a molecular basis for targeting ASH1L and its enzymatic activity to treat MLL-arranged leukemias.
Project description:Deletion (Del) of 17p involving the TP53 tumor suppressor remains an adverse prognostic factor in multiple myeloma, and more effective targeted therapies are needed for these patients. Genomic studies revealed that del17p was associated with reduced copy number and mRNA expression of RNA polymerase II subunit alpha (POLR2A), which is located near TP53. We therefore studied HDP-101, an anti-B-cell maturation antigen (BCMA) antibody drug conjugate (ADC) with the POLR2A poison α-amanitin, which showed potent anti-proliferative and pro-apoptotic activity against cell lines and primary samples. POLR2A knockdown (KD) in both TP53 wild-type (WT) and knockout (KO) cells, with the latter being a model of del17p, enhanced sensitivity to HDP-101 compared to POLR2A WT cells. Gene expression profiling and proteomic studies showed evidence for activation of endoplasmic reticulum stress and the unfolded protein response, as well as a reduction of anti-apoptotic proteins such as Myeloid cell leukemia (MCL)-1. Bortezomib enhanced the activity of HDP-101, as did a gamma-secretase inhibitor, and this ADC overcame resistance both due to microenvironmental factors and in acquired drug resistance models. Finally, HDP-101 was well tolerated in vivo, reduced disease burden with single, 2-4 mg/kg doses, and no evidence of relapse was seen out to 100 days, even in xenografts that modeled del17p through dual TP53 KO/POLR2A KD, which grew more aggressively without treatment. Together, the data validate the efficacy of a new BCMA ADC that is ready for clinical translation, and suggest that it could be equipotent, or perhaps even more effective against myeloma with del17p. We used microarray to investigate the global changes caused by HDP-101 across p53 Wt and p53 KO multiple myeloma cell lines
Project description:To recognize DNA damage, nucleotide excision repair (NER) deploys a multipart mechanism by which the XPC sensor detects helical distortions followed by engagement of TFIIH for lesion verification. Accessory players ensure that this factor handover takes place on chromatin where DNA is wrapped around histones. We show that the histone methyltransferase ASH1L, once activated by MRG15, accelerates global-genome NER activity. Upon UV irradiation, ASH1L deposits H3K4me3 marks all over the genome (except in gene promoters), thus priming chromatin for relocations of XPC from native to damaged DNA. ASH1L further recruits the histone chaperone FACT to UV lesions. In the absence of ASH1L, MRG15 or FACT, XPC persists on damaged DNA without being able to deliver lesions to the TFIIH verifier. We conclude that ASH1L implements repair hotspots whose H3K4me3 and FACT occupancy confers an active promoter-like code and organization of histones that make DNA damage verifiable by the NER machinery.
Project description:The ASH1L lysine methyltransferase plays a critical role in development and is frequently dysregulated in cancer and neurodevelopmental diseases. ASH1L catalyzes mono- and dimethylation of histone H3K36 and contains a set of uncharacterized domains. Here, we report the structure-function relationships of the C-terminal cassette of ASH1L encompassing a bromodomain (BD), a PHD finger and a bromo-associated homology (BAH) domain and show that ASH1L co-localizes with H3K4me3 but not with H3K36me2 at transcription start sites genome-wide and is involved in embryonic stem cell differentiation and transcriptional regulation of differentiation marker genes. Our crystal and NMR structural data provide mechanistic details for the recognition of H3K4me3 by PHD, the DNA binding activities of BD and BAH, and crosstalk among these domains. We show that the PHD-H3K4me3 interaction is inhibitory to the catalytic activity of ASH1L and that the DNA binding function of BAH is necessary for ASH1L engagement with the nucleosome. Our findings suggest a mechanism by which the C-terminus of ASH1L associates with chromatin and provide molecular and structural insights that are essential in therapeutic targeting of ASH1L.