ABSTRACT
Alterations in chromatin structure caused by deregulated epigenetic mechanisms collaborate with underlying genetic lesions to promote cancer. SMARCA4/BRG1, a core component of the SWI/SNF ATP-dependent chromatin-remodelling complex, has been implicated by its mutational spectrum as exerting a tumour-suppressor function in many solid tumours; recently however, it has been reported to sustain leukaemogenic transformation in MLL-rearranged leukaemia in mice. Here we further explore the role of SMARCA4 and the two SWI/SNF subunits SMARCD2/BAF60B and DPF2/BAF45D in leukaemia. We observed the selective requirement for these proteins for leukaemic cell expansion and self-renewal in-vitro as well as in leukaemia. Gene expression profiling in human cells of each of these three factors suggests that they have overlapping functions in leukaemia. The gene expression changes induced by loss of the three proteins demonstrate that they are required for the expression of haematopoietic stem cell associated genes but in contrast to previous results obtained in mouse cells, the three proteins are not required for the expression of c-MYC regulated genes.
Subject(s)
Chromosomal Proteins, Non-Histone/metabolism , DNA Helicases/metabolism , DNA-Binding Proteins/metabolism , Leukemia/pathology , Muscle Proteins/metabolism , Myeloid-Lymphoid Leukemia Protein/genetics , Nuclear Proteins/metabolism , Repressor Proteins/metabolism , Transcription Factors/metabolism , Animals , Cell Cycle , Cell Differentiation , Cell Line, Tumor , Cell Proliferation , Cell Self Renewal , Gene Expression Regulation, Leukemic , Gene Knockdown Techniques , Gene Rearrangement , Leukemia/genetics , Mice , Myeloid Cells/pathology , Protein Subunits/metabolism , Proto-Oncogene Proteins c-myc/genetics , Transcription, GeneticABSTRACT
Jarid1b/KDM5b is a histone demethylase that regulates self-renewal and differentiation in stem cells and cancer; however, its function in hematopoiesis is unclear. Here, we find that Jarid1b is highly expressed in primitive hematopoietic compartments and is overexpressed in acute myeloid leukemias. Constitutive genetic deletion of Jarid1b did not impact steady-state hematopoiesis. In contrast, acute deletion of Jarid1b from bone marrow increased peripheral blood T cells and, following secondary transplantation, resulted in loss of bone marrow reconstitution. Our results reveal that deletion of Jarid1b compromises hematopoietic stem cell (HSC) self-renewal capacity and suggest that Jarid1b is a positive regulator of HSC potential.
Subject(s)
Cell Proliferation/genetics , DNA-Binding Proteins/physiology , Hematopoietic Stem Cells/physiology , Jumonji Domain-Containing Histone Demethylases/physiology , Animals , Cell Differentiation/genetics , Cell Division/genetics , DNA-Binding Proteins/genetics , Hematopoiesis/genetics , Jumonji Domain-Containing Histone Demethylases/genetics , Male , Mice , Mice, KnockoutABSTRACT
Epigenetic regulatory mechanisms are implicated in the pathogenesis of acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL). Recent progress suggests that proteins involved in epigenetic control are amenable to drug intervention, but little is known about the cancer-specific dependency on epigenetic regulators for cell survival and proliferation. We used a mouse model of human AML induced by the MLL-AF9 fusion oncogene and an epigenetic short hairpin RNA (shRNA) library to screen for novel potential drug targets. As a counter-screen for general toxicity of shRNAs, we used normal mouse bone marrow cells. One of the best candidate drug targets identified in these screens was Jmjd1c. Depletion of Jmjd1c impairs growth and colony formation of mouse MLL-AF9 cells in vitro as well as establishment of leukemia after transplantation. Depletion of JMJD1C impairs expansion and colony formation of human leukemic cell lines, with the strongest effect observed in the MLL-rearranged ALL cell line SEM. In both mouse and human leukemic cells, the growth defect upon JMJD1C depletion appears to be primarily due to increased apoptosis, which implicates JMJD1C as a potential therapeutic target in leukemia.
Subject(s)
Jumonji Domain-Containing Histone Demethylases/genetics , Leukemia, Myeloid, Acute/genetics , Oxidoreductases, N-Demethylating/genetics , Animals , Apoptosis/genetics , Cell Line, Tumor , Epigenesis, Genetic , Gene Knockdown Techniques , Genes, myb , Genes, myc , Histone-Lysine N-Methyltransferase/genetics , Humans , Jumonji Domain-Containing Histone Demethylases/antagonists & inhibitors , Leukemia, Experimental/genetics , Leukemia, Experimental/pathology , Leukemia, Myeloid, Acute/pathology , Mice , Myeloid-Lymphoid Leukemia Protein/genetics , Oncogene Proteins, Fusion/genetics , Oxidoreductases, N-Demethylating/antagonists & inhibitors , RNA, Messenger/genetics , RNA, Messenger/metabolism , RNA, Neoplasm/genetics , RNA, Neoplasm/metabolism , RNA, Small Interfering/genetics , Tumor Stem Cell AssayABSTRACT
During mammalian spermatogenesis, the mouse VASA homolog (MVH; also known as DDX4), a germ-cell-specific DEAD-box type RNA-binding protein, localizes in a germline-specific RNA granule termed the chromatoid body (CB). Genetic analyses have revealed that MVH is essential for progression through spermatogenesis, although the molecular mechanisms of its function remain elusive. We found that the acetyltransferase Hat1, and its cofactor, p46, are specifically colocalized with MVH in the CB and acetylate MVH at Lys405, leading to inactivation of its RNA-binding activity. Notably, the acetylation is developmentally regulated, paralleling the temporally regulated colocalization of Hat1 and p46 in the CB. We have identified 858 mRNAs as MVH targets, a large proportion of which correspond to previously known translationally arrested genes. Importantly, eIF4B mRNA, a target of MVH, is selectively released from the MVH-ribonucleoprotein (RNP) complex when MVH is acetylated, paralleling an increase in eIF4B protein. These findings reveal a previously unknown signaling pathway that links acetylation to RNA processing in the control of spermatogenesis.