The C. elegans Twist target gene, arg-1, is regulated by distinct E box promoter elements.
Proper metazoan mesoderm development requires the function of a basic helix-loop-helix (bHLH) transcription factor, Twist. Twist-containing dimers regulate the expression of target genes by binding to E box promoter elements containing the site CANNTG. In Caenorhabditis elegans, CeTwist functions in a subset of mesodermal cells. Our study focuses on how CeTwist controls the expression of its target gene, arg-1. We find that a 385bp promoter region of arg-1, which contains three different E box elements, is sufficient for maintaining the full CeTwist-dependent expression pattern. Interestingly, the expression of arg-1 in different tissues is regulated distinctly, and each of the three E boxes plays a unique role in the regulation. The first and the third E boxes (E1 and E3) are required for expression in a distinct subset of the mesodermal tissues where arg-1 is normally expressed, and the second E box (E2) is required for expression in the full set of those tissues. The essential role of E2 in arg-1 regulation is correlated with the finding that E2 binds with greater affinity than E1 or E3 to CeTwist dimers. A potential role for additional transcription factors in mesodermal gene regulation is suggested by the discovery of a novel site that is also required for arg-1 expression in a subset of the tissues but is not bound in vitro by CeTwist. On the basis of these results, we propose a model of CeTwist gene regulation in which expression is controlled by tissue-specific binding of distinct sets of E boxes.
Zhao
Jie
J
Department of Biology, The Catholic University of America, Washington, DC 20064, USA.
Wang
Peng
P
Corsi
Ann K
AK
D000818:Animals; D030801:Animals, Genetically Modified; D051792:Basic Helix-Loop-Helix Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D017238:Genes, Helminth; D008648:Mesoderm / Q000378:metabolism; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D014018:Tissue Distribution; D051879:Twist-Related Protein 1 / Q000235:genetics / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D029742:Caenorhabditis elegans Proteins; D051879:Twist-Related Protein 1; C106514:HLH-2 protein, C elegans; C497752:HLH-8 protein, C elegans