title: Stem cell gene SALL4 suppresses transcription through recruitment of DNA methyltransferases.
abstract: The stem cell protein SALL4 plays a vital role in maintaining stem cell identity and governing stem cell self-renewal through transcriptional repression. To explore SALL4-mediated mechanisms involved in transcriptional repression, we investigated DNA modifications underlying its regulatory activities. By a luciferase activity assay, we found that both histone deacetylase inhibitor valproic acid (VPA) and DNA methylation inhibitor 5-azacytidine (5-azaC) specifically reversed the repression effect of SALL4 on its own as well as other Sal gene promoter activities. Cotreatment of VPA with 5-azaC in cells almost completely blocked this repression effect. Further co-immunoprecipitation assay and enzyme activity analysis demonstrated that SALL4 protein directly interacted with different DNA methyltransferases (DNMTs) and purified DNMT enzymatic activities from nuclear extracts. In addition, SALL4 isoforms co-occupied the same regions of its own promoter as DNMT corepressors, and ectopic overexpression of SALL4 led to increased CpG island promoter methylation of silenced genes in various cell types. These included primary hematopoietic stem/progenitor cells, fibroblasts, and NB4 leukemic cells. In NB4 cells, treatment of cells with 5-azaC also caused decreased amounts of methylated alleles of SALL4 and PTEN and dramatically increased their mRNA expression. Our studies identify a new mechanism by which SALL4 represses gene expression through interaction with DNMTs. Furthermore, DNMTs and histone deacetylase repressors synergistically contribute to the regulatory effects of SALL4. These findings provide new insights into stem cell self-renewal mediated by SALL4 via epigenetic machinery.
authors: Division of Cancer Biology, Nevada Cancer Institute, Las Vegas, Nevada 89135, USA. jyang@nvcancer.org
authors: Jianchang
authors: J
authors: Yang
authors: Tyler R
authors: TR
authors: Corsello
authors: Yupo
authors: Y
authors: Ma
mesh_terms: D001374:Azacitidine / Q000494:pharmacology; D045744:Cell Line, Tumor; D018899:CpG Islands / Q000502:physiology; D019175:DNA Methylation / Q000187:drug effects / Q000502:physiology*; D015254:DNA Modification Methylases; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D020868:Gene Silencing / Q000187:drug effects / Q000502:physiology*; D057809:HEK293 Cells; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism*; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*; D014635:Valproic Acid / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D012097:Repressor Proteins; C472575:SALL4 protein, human; D014157:Transcription Factors; D014635:Valproic Acid; D015254:DNA Modification Methylases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D006655:Histone Deacetylases; D001374:Azacitidine