Specific Histone Lysine 4 Methylation Patterns Define TR-Binding Capacity and Differentiate Direct T3 Responses

• Published in: Molecular endocrinology (Baltimore, Md.) Vol. 25; no. 2; pp. 225 - 237
• Main Authors: Bilesimo, Patrice, Jolivet, Pascale, Alfama, Gladys, Buisine, Nicolas, Mevel, Sebastien Le, Havis, Emmanuelle, Demeneix, Barbara A., Sachs, Laurent M.
• Format: Journal Article
• Language: English
• Published: United States Oxford University Press 01.02.2011; Endocrine Society
• Subjects: Acetylation; Animals; Animals, Genetically Modified; Basic-Leucine Zipper Transcription Factors - genetics; Chromatin Immunoprecipitation; Gene Expression Regulation, Developmental; Histones - genetics; Histones - metabolism; Larva - genetics; Life Sciences; Methylation; Original Research; Polymerase Chain Reaction; Promoter Regions, Genetic; RNA Polymerase II - metabolism; Thyroid Hormone Receptors beta - genetics; Thyroid Hormone Receptors beta - metabolism; Transcription, Genetic; Triiodothyronine - metabolism; Xenopus; Xenopus tropicalis; TR-α | TR-β; Thyroid hormone
• ISSN: 0888-8809; 1944-9917; 1944-9917; 0888-8809
• DOI: 10.1210/me.2010-0269

Abstract The diversity of thyroid hormone T3 effects in vivo makes their molecular analysis particularly challenging. Indeed, the current model of the action of T3 and its receptors on transcription does not reflect this diversity. Here, T3-dependent amphibian metamorphosis was exploited to investigate, in an in vivo developmental context, how T3 directly regulates gene expression. Two, direct positively regulated T3-response genes encoding transcription factors were analyzed: thyroid hormone receptor β (TRβ) and TH/bZIP. Reverse transcription-real-time quantitative PCR analysis on Xenopus tropicalis tadpole brain and tail fin showed differences in expression levels in premetamorphic tadpoles (lower for TH/bZIP than for TRβ) and differences in induction after T3 treatment (lower for TRβ than for TH/bZIP). To dissect the mechanisms underlying these differences, chromatin immunoprecipitation was used. T3 differentially induced RNA polymerase II and histone tail acetylation as a function of transcriptional level. Gene-specific patterns of TR binding were found on the different T3 -responsive elements (higher for TRβ than for TH/bZIP), correlated with gene-specific modifications of H3K4 methylation (higher for TRβ than for TH/bZIP). Moreover, tissue-specific modifications of H3K27 were found (lower in brain than in tail fin). This first in vivo analysis of the association of histone modifications and TR binding/gene activation during vertebrate development for any nuclear receptor indicate that chromatin context of thyroid-responsive elements loci controls the capacity to bind TR through variations in histone H3K4 methylation, and that the histone code, notably H3, contributes to the fine tuning of gene expression that underlies complex physiological T3 responses.