title: Caudal-like PAL-1 directly activates the bodywall muscle module regulator hlh-1 in C. elegans to initiate the embryonic muscle gene regulatory network.
abstract: Previous work in C. elegans has shown that posterior embryonic bodywall muscle lineages are regulated through a genetically defined transcriptional cascade that includes PAL-1/Caudal-mediated activation of muscle-specific transcription factors, including HLH-1/MRF and UNC-120/SRF, which together orchestrate specification and differentiation. Using chromatin immunoprecipitation (ChIP) in embryos, we now demonstrate direct binding of PAL-1 in vivo to an hlh-1 enhancer element. Through mutational analysis of the evolutionarily conserved sequences within this enhancer, we identify two cis-acting elements and their associated transacting factors (PAL-1 and HLH-1) that are crucial for the temporal-spatial expression of hlh-1 and proper myogenesis. Our data demonstrate that hlh-1 is indeed a direct target of PAL-1 in the posterior embryonic C. elegans muscle lineages, defining a novel in vivo binding site for this crucial developmental regulator. We find that the same enhancer element is also a target of HLH-1 positive auto regulation, underlying (at least in part) the sustained high levels of CeMyoD in bodywall muscle throughout development. Together, these results provide a molecular framework for the gene regulatory network activating the muscle module during embryogenesis.
authors.affiliation: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Lei
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Tetsunari
authors.initials: T
authors.lastname: Fukushige
authors.forename: Andrew
authors.initials: A
authors.lastname: Fire
authors.forename: Michael
authors.initials: M
authors.lastname: Krause
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000235:genetics* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism; D019143:Evolution, Molecular; D018507:Gene Expression Regulation, Developmental; D053263:Gene Regulatory Networks / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009124:Muscle Proteins; D009132:Muscles / Q000196:embryology* / Q000378:metabolism; D018006:Myogenic Regulatory Factors / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins; D011485:Protein Binding; D016415:Sequence Alignment; D013379:Substrate Specificity; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D015533:Transcriptional Activation / Q000235:genetics
chemical_list: D029742:Caenorhabditis elegans Proteins; D018398:Homeodomain Proteins; D009124:Muscle Proteins; D018006:Myogenic Regulatory Factors; D009687:Nuclear Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C066645:HLH-1 protein, C elegans; C068665:pal-1 protein, C elegans