title: Secondary enhancers synergise with primary enhancers to guarantee fine-tuned muscle gene expression.
abstract: Although tight quantitative control of gene expression is required to ensure that organs and tissues function correctly, the transcriptional mechanisms underlying this process still remain poorly understood. Here, we describe novel and evolutionary conserved secondary enhancers that are needed for the regulation of the expression of Troponin I genes. Secondary enhancers are silent when tested individually in electroporated muscles but interact with the primary enhancers and are required to precisely control the appropriate timing, the tissue and fibre specificity, and the quantitative expression of these genes during muscle differentiation. Synergism is completely dependent of the fully conserved MEF2 site present on the primary enhancers core of skeletal muscle Troponin I genes. Thus, while each of these paired enhancers has a different function, the concerted action of both is crucial to recapitulate endogenous gene expression. Through comparative genomics, we predict that this mechanism has also arisen in other mammalian muscle genes. Our results reveal the existence of a novel mechanism, conserved from flies to mammals, to fine-tune gene expression in each muscle and probably other tissues.
authors.affiliation: Departamento de Bioquímica & Instituto Investigaciones Biomédicas, Facultad de Medicina, UAM-CSIC, Spain.
authors.forename: Lucia
authors.initials: L
authors.lastname: Guerrero
authors.forename: Raquel
authors.initials: R
authors.lastname: Marco-Ferreres
authors.forename: Antonio L
authors.initials: AL
authors.lastname: Serrano
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Arredondo
authors.forename: Margarita
authors.initials: M
authors.lastname: Cervera
mesh_terms: D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D017124:Conserved Sequence; D004742:Enhancer Elements, Genetic / Q000502:physiology*; D005786:Gene Expression Regulation; D007763:Lac Operon; D064326:MEF2 Transcription Factors; D008297:Male; D051379:Mice; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018006:Myogenic Regulatory Factors / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D019210:Troponin I / Q000235:genetics*
chemical_list: D064326:MEF2 Transcription Factors; C578036:Mef2a protein, mouse; D018006:Myogenic Regulatory Factors; D019210:Troponin I