title: Bypassing the requirements for epigenetic modifications in gene transcription by increasing enhancer strength.
abstract: Our current concept postulates that histone acetylation is required for the recruitment of bromodomain-containing transcription complexes, such as the chromatin-remodeling machine SWI/SNF and the basal transcription factor TFIID. We generated simple NF-kappaB-dependent enhancers of increasing transcriptional strengths and found that the histone acetylation requirements for activation of transcription depended on the strengths of these enhancers. All enhancers function by recruiting SWI/SNF and TFIID to induce nucleosome sliding, a prerequisite for transcriptional activation. However, histone acetylation, although it occurs, is dispensable for TFIID and SWI/SNF recruitment by the strong enhancers, indicating that strong activators can overcome the chromatin barrier by directly recruiting the necessary transcriptional complexes. Weak enhancers depend on histone acetylation for recruitment, and this requirement is independent of a histone acetylation code. Thus, the need for nucleosome modifications is imposed on genes and translated according to the quality and strengths of the activators.
authors.affiliation: Institute of Molecular Biology, Genetics, and Biotechnology, Foundation for Biomedical Research of the Academy of Athens, 4 Soranou Efesiou Street, Athens 11527, Greece.
authors.forename: George
authors.initials: G
authors.lastname: Koutroubas
authors.forename: Menie
authors.initials: M
authors.lastname: Merika
authors.forename: Dimitris
authors.initials: D
authors.lastname: Thanos
mesh_terms: D000107:Acetylation; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D004742:Enhancer Elements, Genetic / Q000235:genetics / Q000502:physiology*; D044127:Epigenesis, Genetic; D006367:HeLa Cells; D006657:Histones; D006801:Humans; D016328:NF-kappa B; D009707:Nucleosomes / Q000378:metabolism; D035362:Transcription Factor TFIID / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics*; D015533:Transcriptional Activation / Q000235:genetics*; D014162:Transfection
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D006657:Histones; D016328:NF-kappa B; D009707:Nucleosomes; C445179:SWI-SNF-B chromatin-remodeling complex; D035362:Transcription Factor TFIID; D014157:Transcription Factors