Epigenetic regulation of thy-1 by histone deacetylase inhibitor in rat lung fibroblasts.
Thy-1 is a cell surface glycoprotein present on normal lung fibroblasts but absent from the fibroblastic foci of idiopathic pulmonary fibrosis. Thy-1 correlates inversely with fibrogenic phenotypic characteristics and functions as a "fibrosis suppressor." Promoter region hypermethylation can silence Thy-1 expression in fibroblastic foci, suggesting that epigenetic regulation is important in programming the fibrotic phenotype. We examined whether histone modifications are important in regulating Thy-1 expression in lung fibroblasts. Treatment with the histone deacetylase inhibitor trichostatin A (TSA) restored Thy-1 expression in Thy-1(-) cells in a time-dependent and concentration-dependent fashion and was associated with enrichment of histone acetylation. Chromatin immunoprecipitation demonstrated Thy-1 depletion of trimethylated H3K27 after 24 hours of TSA treatment, concurrent with enrichment of trimethylated H3K4 and acetylated H4. Bisulfite sequencing of the Thy-1 promoter region revealed demethylation of the previously hypermethylated CpG sites after treatment with TSA. Although Thy-1 was hypermethylated in Thy-1(-) lung fibroblasts, we observed that Thy-1(-) cells have lower global DNA methylation compared with Thy-1(+) lung fibroblasts, which was partially reversed by TSA treatment. TSA treatment up-regulates total methyltransferase activity in these cells. Our data indicate that Thy-1 silencing is regulated by histone modifications in addition to promoter hypermethylation in lung fibroblasts. Additionally, our findings indicate that alteration of histone modifications alters DNA methylation. Understanding the molecular hierarchy of events with respect to reactivation of transcription and reversal of histone modification will be critical to understand and modify the regulated expression of Thy-1, a tumor-supressor and fibrosis-suppressor gene.
Sanders
Yan Y
YY
Department of Pediatrics, University of California-San Diego, 9500 Gilman Dr., MC 0731, San Diego, CA 92093-0731, USA.
Tollefsbol
Trygve O
TO
Varisco
Brian M
BM
Hagood
James S
JS
D000818:Animals; D002478:Cells, Cultured; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation / Q000187:drug effects / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D044127:Epigenesis, Genetic; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D020868:Gene Silencing; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D006877:Hydroxamic Acids / Q000494:pharmacology*; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008745:Methylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D011499:Protein Processing, Post-Translational / Q000187:drug effects* / Q000235:genetics; D011658:Pulmonary Fibrosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051381:Rats; D018800:Thy-1 Antigens / Q000096:biosynthesis* / Q000235:genetics; D013997:Time Factors; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis* / Q000235:genetics
D056572:Histone Deacetylase Inhibitors; D006657:Histones; D006877:Hydroxamic Acids; D018800:Thy-1 Antigens; D025521:Tumor Suppressor Proteins; C012589:trichostatin A