title: Transforming Growth Factor-β1 Increases DNA Methyltransferase 1 and 3a Expression through Distinct Post-transcriptional Mechanisms in Lung Fibroblasts.
abstract: DNA methylation is a fundamental epigenetic mark that plays a critical role in differentiation and is mediated by the actions of DNA methyltransferases (DNMTs). TGF-β1 is one of the most potent inducers of fibroblast differentiation, and although many of its actions on fibroblasts are well described, the ability of TGF-β1 to modulate DNA methylation in mesenchymal cells is less clear. Here, we examine the ability of TGF-β1 to modulate the expression of various DNMTs in primary lung fibroblasts (CCL210). TGF-β1 increased the protein expression, but not RNA levels, of both DNMT1 and DNMT3a. The increases in DNMT1 and DNMT3a were dependent on TGF-β1 activation of focal adhesion kinase and PI3K/Akt. Activation of mammalian target of rapamycin complex 1 by Akt resulted in increased protein translation of DNMT3a. In contrast, the increase in DNMT1 by TGF-β1 was not dependent on new protein synthesis and instead was due to decreased protein degradation. TGF-β1 treatment led to the phosphorylation and inactivation of glycogen synthase kinase-3β, which resulted in inhibition of DNMT1 ubiquitination and proteosomal degradation. The phosphorylation and inactivation of glycogen synthase kinase-3β was dependent on mammalian target of rapamycin complex 1. These results demonstrate that TGF-β1 increases expression of DNMT1 and DNMT3a through different post-transcriptional mechanisms. Because DNA methylation is critical to many processes including development and differentiation, for which TGF-β1 is known to be crucial, the ability of TGF-β1 to increase expression of both DNMT1 and DNMT3a demonstrates a novel means by which TGF-β1 may regulate DNA methylation in these cells.
authors.affiliation: From the Division of Pulmonary and Critical Care Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109.
authors.forename: Hailey B
authors.initials: HB
authors.lastname: Koh
authors.affiliation: From the Division of Pulmonary and Critical Care Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Scruggs
authors.affiliation: From the Division of Pulmonary and Critical Care Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109 stehuang@umich.edu.
authors.forename: Steven K
authors.initials: SK
authors.lastname: Huang
mesh_terms: D002460:Cell Line; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000096:biosynthesis* / Q000235:genetics; D019175:DNA Methylation / Q000502:physiology; D000090205:DNA Methyltransferase 3A; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D000071679:Glycogen Synthase Kinase 3 beta / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008168:Lung / Q000166:cytology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis / Q000502:physiology*; D059748:Proteolysis; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D000071679:Glycogen Synthase Kinase 3 beta; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D053773:Transforming Growth Factor beta1; C000717967:DNMT3A protein, human; C508960:TGFB1 protein, human; C000619380:DNMT1 protein, human; C000605506:GSK3B protein, human
keywords: Akt PKB; DNA methylation; DNA methyltransferase; DNMT1; DNMT3a; fibroblast; glycogen synthase kinase 3 (GSK-3); mammalian target of rapamycin (mTOR); transforming growth factor beta (TGF-B); ubiquitylation (ubiquitination)