The C. elegans sex determination gene,
tra-2 , encodes a large transmembrane protein that is required for female sexual development. Repression of
tra-2 translation is necessary for male cell fate development in both somatic and germ line tissues. Two elements located in the 3'UTR of the
tra-2 mRNA, called TGEs, are required for
tra-2 translational regulation. GLD-1 is a member of the STAR family of RNA binding proteins and regulates
tra-2 translation in the hermaphrodite germline to permit spermatogenesis. However, translational regulation of
tra-2 also occurs in the soma. The STAR family contains an approximately 200 amino acid domain (STAR domain) that is highly conserved, raising the possibility that another STAR protein represses
tra-2 in the soma. The C. elegans sequencing project has identified at least five predicted open reading frames that have strong similarity to GLD-1. We have preliminary evidence that suggests at least one of these five STAR proteins, T21G5.5, can regulate translation through the
tra-2 3'UTR. T21G5.5 is 67% identical to GLD-1 at the amino acid level within the STAR domain. I have performed RNA-mediated interference (RNAi) of T21G5.5 in transgenic C. elegans animals that carry a reporter transgene encoding the lacZ gene with the wild type
tra-2 3'UTR. The F1 progeny following RNAi of T21G5.5 had an increased level of b -gal staining in the soma compared to wild type transgenic animals. 22% of the RNAi animals had b -gal activity in intestinal cells compared to 12.5% of non-injected. In addition, animals that stained for b -gal after injection with T21G5.5 also showed an increase in the number of b -gal stained intestinal cells (2-8 cells) compared to wild type (1-2 cells). Disruption of T21G5.5 activity also resulted in animals with interesting morphological phenotypes. F1 animals had a dumpy phenotype and an altered tail morphology. In addition, the gonads of these animals were sexually transformed. These preliminary data suggest that T21G5.5 is a likely candidate for a TGE-dependent translational repressor. However, these results do not eliminate the possibility that other STAR proteins are also 3'UTR-dependent translational regulators. We are currently testing this possibility.