RNA-binding proteins.

The C. elegans genome encodes many RNA-binding proteins (RBPs) with diverse functions in development, indicative of extensive layers of post-transcriptional control of RNA metabolism. A number of C. elegans RBPs have been identified by forward or reverse genetics. They tend to display tissue-specific mutant phenotypes, which underscore their functional importance. In addition, several RBPs that bind regulatory sequences in the 3'untranslated regions of mRNAs have been identified molecularly. Most C. elegans RBPs are conserved throughout evolution, suggesting that their study in C. elegans may uncover new conserved biological functions. In this review, we primarily discuss RBPs that are associated with well-characterized mutant phenotypes in the germ line, the early embryo, or in somatic tissues. We also discuss the identification of RNA targets of RBPs, which is an important first step to understand how an RBP controls C. elegans development. It is likely that most RBPs regulate multiple RNA targets. Once multiple RNA targets are identified, specific features that distinguish target from non-target RNAs and the type(s) of RNA metabolism that each RBP controls can be determined. Furthermore, one can determine whether the RBP regulates all targets by the same mechanism or different targets by distinct mechanisms. Such studies will provide insights into how RBPs exert coordinate control of their RNA targets, thereby affecting development in a concerted fashion.