The STAR protein, GLD-1, is a translational regulator of sexual identity in Caenorhabditis elegans

The Caenorhabditis elegans sex determination gene, tra-2, is translationally regulated by elements in the 3'-untranslated region called TGEs. TGEs govern the translation of mRNAs in both invertebrates and vertebrates, indicating that this is a highly conserved mechanism for controlling gene activity. A factor called DRF, found in worm extracts binds the TGEs and may be a repressor of translation. Using the yeast three-hybrid screen and RNA gel shift analysis, we have found that the protein GLD-1, a germline-specific protein and a member of the STAR family of RNA-binding proteins, specifically binds to the TGEs. GLD-1 is essential for oogenesis, and is also necessary for spermatogenesis and inhibition of germ cell proliferation. Several lines of evidence demonstrate that GLD-1 is a translational repressor acting through the TGEs to repress tra-2 translation. GLD-1 can repress the translation of reporter RNAs via the TGEs both in vitro and in vivo, and is required to maintain low TRA-2A protein levels in the germline. Genetic analysis indicates that GLD-1 acts upstream of the TGE control. Finally, we show that endogenous GLD-1 is a component of DRF. The conservation of the TGE control and the STAR family suggests that at least a subset of STAR proteins may work through the TGEs to control translation.