The mec-3 gene contains cis-acting elements mediating positive and negative regulation in cells produced by asymmetric cell division in Caenorhabditis elegans.
The homeo box-containing genes mec-3 and unc-86 are necessary to specify the fate of a defined set of mechanoreceptors in Caenorhabditis elegans. Previous experiments have shown that mec-3 expression can be divided into two phases: initial synthesis mediated in part by unc-86, and continued synthesis that requires mec-3 itself. We now identify sequences that have been conserved during Caenorhabditis evolution and are necessary for establishment, maintenance, and repression of mec-3 expression. Upstream of the start codon for the mec-3-coding sequence are four segments (regions I-IV) of 71, 29, 28, and 24 bp, which are almost identical between C. elegans and Caenorhabditis vulgarensis. Region I is the only conserved sequence that effects establishment of mec-3 synthesis. Maintenance of mec-3 expression is mediated primarily by region II. Repression appears to be controlled by several segments: Mutation of region III, region IV, and parts of region I in a mec-3-lacZ fusion results in beta-galactosidase expression in some non-mec-3-expressing sisters of mec-3-positive cells. These results indicate that the mec-3 5' region contains target sequences that mediate a genetic switch between alternative fates expressed by sister cells in a stereotyped cell lineage.
Department of Biology, Rutgers University, Piscataway, New Jersey 08855-1059.
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002107:Caenorhabditis / Q000166:cytology / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins; D002455:Cell Division / Q000235:genetics; D004247:DNA; D005786:Gene Expression Regulation; D005801:Genes, Homeobox; D005812:Genes, Switch; D015801:Helminth Proteins / Q000235:genetics*; D060850:LIM-Homeodomain Proteins; D008465:Mechanoreceptors / Q000166:cytology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000235:genetics; D014157:Transcription Factors; D001616:beta-Galactosidase / Q000235:genetics
D029742:Caenorhabditis elegans Proteins; D015801:Helminth Proteins; D060850:LIM-Homeodomain Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C072005:mec-3 protein, C elegans; D004247:DNA; D001616:beta-Galactosidase