title: Functional studies of the Ciona intestinalis myogenic regulatory factor reveal conserved features of chordate myogenesis.
abstract: Ci-MRF is the sole myogenic regulatory factor (MRF) of the ascidian Ciona intestinalis, an invertebrate chordate. In order to investigate its properties we developed a simple in vivo assay based on misexpressing Ci-MRF in the notochord of Ciona embryos. We used this assay to examine the roles of three structural motifs that are conserved among MRFs: an alanine-threonine (Ala-Thr) dipeptide of the basic domain that is known in vertebrates as the myogenic code, a cysteine/histidine-rich (C/H) domain found just N-terminal to the basic domain, and a carboxy-terminal amphipathic α-helix referred to as Helix III. We show that the Ala-Thr dipeptide is necessary for normal Ci-MRF function, and that while eliminating the C/H domain or Helix III individually has no demonstrable effect on Ci-MRF, simultaneous loss of both motifs significantly reduces its activity. Our studies also indicate that direct interaction between CiMRF and an essential E-box of Ciona Troponin I is required for the expression of this muscle-specific gene and that multiple classes of MRF-regulated genes exist in Ciona. These findings are consistent with substantial conservation of MRF-directed myogenesis in chordates and demonstrate for the first time that the Ala/Thr dipeptide of the basic domain of an invertebrate MRF behaves as a myogenic code.
authors: Department of Biology, Rhode Island College, Providence, RI 02908, USA.
authors: Stephanie A
authors: SA
authors: Izzi
authors: Bonnie J
authors: BJ
authors: Colantuono
authors: Kelly
authors: K
authors: Sullivan
authors: Parul
authors: P
authors: Khare
authors: Thomas H
authors: TH
authors: Meedel
mesh_terms: D000409:Alanine / Q000235:genetics; D000818:Animals; D043344:Chordata / Q000235:genetics; D002938:Ciona intestinalis / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D008954:Models, Biological; D024510:Muscle Development; D009132:Muscles / Q000378:metabolism; D009154:Mutation; D018006:Myogenic Regulatory Factors / Q000235:genetics / Q000502:physiology*; D009672:Notochord / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013912:Threonine / Q000235:genetics
chemical_list: D018006:Myogenic Regulatory Factors; D010455:Peptides; D013912:Threonine; D000409:Alanine
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