title: Coordination of ges-1 expression between the Caenorhabditis pharynx and intestine.
abstract: We have previously shown that the Caenorhabditis elegans gut-specific esterase gene (Ce-ges-1) has the unusual ability to be expressed in different modules of the embryonic digestive tract (anterior pharynx, posterior pharynx, and rectum) depending on sequence elements within the Ce-ges-1 promoter. In the present paper, we analyze the expression of the ges-1 homolog (Cb-ges-1) from the related nematode Caenorhabditis briggsae and show that Cb-ges-1 also has the ability to switch expression between gut and pharynx + rectum. The control of this expression switch centres on a tandem pair of WGATAR sites in the Cb-ges-1 5'-flanking region, just as it does in Ce-ges-1. We use sequence alignments and subsequent deletions to identify a region at the 3'-end of both Ce-ges-1 and Ce-ges-1 that acts as the ges-1 cryptic pharynx enhancer whose activity is revealed by removal of the 5' WGATAR sites. This region contains a conserved binding site for PHA-4 (the C. elegans ortholog of forkhead/HNF3 alpha, beta,gamma factors), which is expressed in all cells of the developing pharynx and a subset of cells of the developing rectum. We propose a model in which the normal expression of ges-1 is controlled by the gut-specific GATA factor ELT-2. We propose that, in the pharynx (and rectum), PHA-4 is normally bound to the ges-1 3'-enhancer sequence but that the activation function of PHA-4 is kept repressed by a (presently unknown) factor binding in the vicinity of the 5' WGATAR sites. We suggest that this control circuitry is maintained in Caenorhabditis because pharyngeal expression of ges-1 is advantageous only under certain developmental or environmental conditions.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
authors.forename: S D
authors.initials: SD
authors.lastname: Marshall
authors.forename: J D
authors.initials: JD
authors.lastname: McGhee
mesh_terms: D000818:Animals; D001483:Base Sequence; D001757:Blastomeres / Q000378:metabolism; D002107:Caenorhabditis; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins; D002265:Carboxylic Ester Hydrolases / Q000096:biosynthesis*; D019070:Cell Lineage; D050980:GATA Transcription Factors; D017353:Gene Deletion; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000196:embryology*; D008164:Luminescent Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D010614:Pharynx / Q000196:embryology* / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012329:RNA, Bacterial / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012007:Rectum / Q000196:embryology; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction; D013045:Species Specificity; D013997:Time Factors; D015534:Trans-Activators / Q000096:biosynthesis / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; C094134:ELT-2 protein, C elegans; D050980:GATA Transcription Factors; D008164:Luminescent Proteins; C113277:Pha-4 protein, C elegans; C042027:RNA I; D012329:RNA, Bacterial; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; D002265:Carboxylic Ester Hydrolases; C095990:ges-1 protein, C elegans; D001616:beta-Galactosidase