ABSTRACT
Epigenetic gene silencing by histone modifications and DNA methylation is essential for cancer development. The molecular mechanism that promotes selective epigenetic changes during tumorigenesis is not understood. We report here that the PIAS1 SUMO ligase is involved in the progression of breast tumorigenesis. Elevated PIAS1 expression was observed in breast tumor samples. PIAS1 knockdown in breast cancer cells reduced the subpopulation of tumor-initiating cells, and inhibited breast tumor growth in vivo. PIAS1 acts by delineating histone modifications and DNA methylation to silence the expression of a subset of clinically relevant genes, including breast cancer DNA methylation signature genes such as cyclin D2 and estrogen receptor, and breast tumor suppressor WNT5A. Our studies identify a novel epigenetic mechanism that regulates breast tumorigenesis through selective gene silencing.
Subject(s)
Breast Neoplasms/genetics , Breast Neoplasms/pathology , Breast/pathology , Carcinogenesis/genetics , Epigenesis, Genetic/genetics , Protein Inhibitors of Activated STAT/genetics , Small Ubiquitin-Related Modifier Proteins/genetics , Animals , Cell Line, Tumor , Cyclin D2/genetics , DNA Methylation/genetics , Female , Gene Expression Regulation, Neoplastic/genetics , Gene Silencing , Humans , Mice, SCID , Proto-Oncogene Proteins/genetics , Receptors, Estrogen/genetics , Ubiquitin-Protein Ligases/genetics , Wnt Proteins/genetics , Wnt-5a ProteinABSTRACT
The selective and temporal DNA methylation plays an important role in the self-renewal and differentiation of hematopoietic stem cells (HSCs), but the molecular mechanism that controls the dynamics of DNA methylation is not understood. Here, we report that the PIAS1 epigenetic pathway plays an important role in regulating HSC self-renewal and differentiation. PIAS1 is required for maintaining the quiescence of dormant HSCs and the long-term repopulating capacity of HSC. Pias1 disruption caused the abnormal expression of lineage-associated genes. Bisulfite sequencing analysis revealed the premature promoter demethylation of Gata1, a key myeloerythroid transcription factor and a PIAS1-target gene, in Pias1(-/-) HSCs. As a result, Pias1 disruption caused the inappropriate induction of Gata1 in HSCs and common lymphoid progenitors (CLPs). The expression of other myeloerythroid genes was also enhanced in CLPs and lineage-negative progenitors, with a concurrent repression of B cell-specific genes. Consistently, Pias1 disruption caused enhanced myeloerythroid, but reduced B lymphoid lineage differentiation. These results identify a novel role of PIAS1 in maintaining the quiescence of dormant HSCs and in the epigenetic repression of the myeloerythroid program.
Subject(s)
Cell Differentiation/genetics , Cell Proliferation , Hematopoietic Stem Cells/physiology , Protein Inhibitors of Activated STAT/physiology , Animals , Bone Marrow Cells/physiology , Cell Lineage/genetics , Cell Movement/genetics , Cellular Microenvironment/genetics , Epigenesis, Genetic , Mice , Mice, Inbred C57BL , Mice, Knockout , Stem Cell Niche/geneticsABSTRACT
CD4(+)Foxp3(+) regulatory T (T(reg)) cells are important for maintaining immune tolerance. Understanding the molecular mechanism that regulates T(reg) differentiation will facilitate the development of effective therapeutic strategies against autoimmune diseases. We report here that the SUMO E3 ligase PIAS1 restricts the differentiation of natural T(reg) cells by maintaining a repressive chromatin state of the Foxp3 promoter. PIAS1 acts by binding to the Foxp3 promoter to recruit DNA methyltransferases and heterochromatin protein 1 for epigenetic modifications. Pias1 deletion caused promoter demethylation, reduced histone H3 methylation at Lys(9), and enhanced promoter accessibility. Consistently, Pias1(-/-) mice displayed an increased natural T(reg) cell population and were resistant to the development of experimental autoimmune encephalomyelitis. Our studies have identified an epigenetic mechanism that negatively regulates the differentiation of natural T(reg) cells.
Subject(s)
Epigenesis, Genetic , Lymphopoiesis/genetics , Protein Inhibitors of Activated STAT/physiology , Repressor Proteins/physiology , T-Lymphocytes, Regulatory/cytology , Ubiquitin-Protein Ligases/physiology , Animals , Binding Sites , CD4-Positive T-Lymphocytes/cytology , Chromatin/metabolism , DNA (Cytosine-5-)-Methyltransferases/metabolism , DNA Methylation , DNA Methyltransferase 3A , Encephalomyelitis, Autoimmune, Experimental/immunology , Female , Forkhead Transcription Factors/genetics , Histones/metabolism , Male , Mice , Mice, Inbred C57BL , Mice, Inbred Strains , Promoter Regions, Genetic , T-Lymphocytes, Regulatory/immunology , DNA Methyltransferase 3BABSTRACT
Maintenance of single-layered endothelium, squamous endothelial cell shape, and formation of a patent vascular lumen all require defined endothelial cell polarity. Loss of beta1 integrin (Itgb1) in nascent endothelium leads to disruption of arterial endothelial cell polarity and lumen formation. The loss of polarity is manifested as cuboidal-shaped endothelial cells with dysregulated levels and mislocalization of normally polarized cell-cell adhesion molecules, as well as decreased expression of the polarity gene Par3 (pard3). beta1 integrin and Par3 are both localized to the endothelial layer, with preferential expression of Par3 in arterial endothelium. Luminal occlusion is also exclusively noted in arteries, and is partially rescued by replacement of Par3 protein in beta1-deficient vessels. Combined, our findings demonstrate that beta1 integrin functions upstream of Par3 as part of a molecular cascade required for endothelial cell polarity and lumen formation.
