In vitro and in vivo characterization of Caenorhabditis elegans PHA-4/FoxA response elements.

Caenorhabditis elegans PHA-4 is a member of the FoxA group of transcription factors. PHA-4 is critical for development of the C. elegans pharynx and directly regulates most or all pharyngeal genes. The consensus binding site of PHA-4 has not been identified, with previous analysis of PHA-4 targets relying on the mammalian FoxA consensus. Here, we use in vitro and in vivo analyses to demonstrate three features of PHA-4 response elements. First, the PHA-4 consensus matches that of other FoxA proteins, but only a subset of possible sites is active in an in vivo assay. Second, sequence flanking the core PHA-4 site can influence the strength of reporter expression in vivo, as seen for other Fox proteins. Third, in the context of some pharyngeal promoters, PHA-4 response elements are flanked by distinct cis-regulatory elements that modulate response to PHA-4, generating gene expression in specific pharyngeal cell types.