title: Novel cis-element in intron 1 represses somite expression of zebrafish myf-5.
abstract: Myf-5 is a basic helix-loop-helix (bHLH) transcription factor that controls muscle differentiation. During early embryogenesis, myf-5 expression is transient, somite- and stage-specific. However, the negative regulation of myf-5 is poorly understood. We constructed a plasmid [(-9977/-1)/E1/I1/E2/GFP] that contains the sequence -9977 to -1, exon 1 (E1), intron 1 (I1), and exon 2 (E2) of zebrafish (Danio rerio) myf-5 and a reporter GFP gene. This plasmid was microinjected into zebrafish zygotes. Surprisingly, the somite-specific expression rate of reporter GFP in the transgenic embryos was extremely low (2%, n=392), compared to that of (-9977/-1)/GFP (92%, n=210). Dramatic repression of myf-5 expression was also observed in embryos microinjected with plasmids in which the sequence -8600/-1, -2937/-1 or -290/-1 was linked to E1/I1/E2/GFP. Thus, intron 1 contains a silencer that specifically represses the activity of myf-5. Functional analysis of intron 1 showed a strong, negative, cis-regulatory element was located at +502/+835. Its function was orientation- and position-dependent. The repressive capability of this silencer was completely dependent on two core motifs, IE1 (+502/+527) and IE2 (+816/+835), and a 156-bp spanning sequence that lies between them. This is the first study to identify a novel, cis-acting silencer in intron 1 that is crucial to negatively regulating zebrafish myf-5 expression.
authors.affiliation: Institute of Molecular and Cellular Biology, National Taiwan University, Room 307A, Fisheries Science Building, 1 Roosevelt Road, Section 4, Taipei 106, Taiwan.
authors.forename: Cheng-Yung
authors.initials: CY
authors.lastname: Lin
authors.forename: Yau-Hung
authors.initials: YH
authors.lastname: Chen
authors.forename: Hung-Chieh
authors.initials: HC
authors.lastname: Lee
authors.forename: Huai-Jen
authors.initials: HJ
authors.lastname: Tsai
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000378:metabolism; D047108:Embryonic Development; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins; D017403:In Situ Hybridization; D007438:Introns / Q000235:genetics*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008845:Microinjections; D008856:Microscopy, Fluorescence; D010957:Plasmids / Q000008:administration & dosage / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D019170:Somites / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology / Q000235:genetics*; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D029961:Zebrafish Proteins; D049452:Green Fluorescent Proteins