PES-1 [pattern expression site] is a putative transcription factor expressed in the early C. elegans embryo that shows homology to the fork head family of DNA binding proteins [FDPs]. Mutagenesis with the transposable element Tc1 is being used to generate a mutant phenotype for the
pes-1 gene. PES-1 is a highly diverged member of the fork head family and it is proposed that it defines a new subgroup within this family. A combination of PCR based and hybridisation screens are being used, to identify homologues of
pes-1, to investigate this possibility. We have received the strain NL717 from Ronald Plasterk's group, which contains a Tc1 insertion in the large intron of the
pes-1 gene. A screen is currently in progress to identify deletions in the
pes-1 gene, arising from excision of the Tc1 element. Through this method we should obtain knockouts of the
pes-1 gene, and therefore identify any mutant phenotype, and subsequently be able to further analyse gene function. PES-1 shows only 44% amino acid identity in the putative DNA binding domain with other members of the fork head family. This divergence cannot be explained by it being a C. elegans gene, since two other FDPs have been identified in C. elegans;
lin-31 which specifies three alternative vulval fates, identified by Leilani Miller and Stuart Kim; and
cfh-1 identified by Marie Azzaria, Barbara Goszczynski and Jim McGhee - both show good homology to the other FDPs. Since
pes-1 shows such reduced homology and does not belong to any established subgroup of FDPs, we propose that it may be the founding member of a new subgroup within the fork head family. Degenerate primers were designed to highly conserved regions of the fork head domain focusing on amino acid residues believed to be diagnostic of PES-1. These primers were used in a PCR screen to identify homologues of
pes-1, initially using C. elegans genomic DNA. A number of positive results were obtained which are currently being analysed. A new C. elegans gene showing homology to the fork head family has been identified using this approach and is now being characterised.