Identification of C. elegans DAF-12-binding sites, response elements, and target genes

Intracellular receptor DAF-12 regulates dauer formation and developmental age and affects Caenorhabditis elegans lifespan. Genetic analyses place DAF-12 at the convergence of several signal transduction pathways; however, the downstream effectors and the molecular basis for the receptor's multiple physiological outputs are unknown. Beginning with C. elegans genomic DNA, we devised a procedure for multiple rounds of selection and amplification that yielded fragments bearing DAF-12-binding sites. These genomic fragments mediated DAF-12-dependent transcriptional regulation both in Saccharomyces cerevisiae and in C. elegans; that is, they served as functional DAF-12 response elements. We determined that most of the genomic fragments that displayed DAF-12 response element activity in yeast were linked to genes that were regulated by DAF-12 in C. elegans; indeed, the response element-containing fragments typically resided within clusters of DAF-12-regulated genes. DAF-12 target gene regulation was developmental program and stage specific, potentially predicting a fit of these targets into regulatory networks governing aspects of C. elegans reproductive development and dauer formation.