Germ granules (P granules in C. elegans) are germ-cell-specific cytoplasmic organelles that contain RNAs and proteins. Their molecular functions, which are required for germ cell specification, probably include the regulation of mRNA expression. On , Spike and colleagues provide new insights into this possible function by characterizing a new gene, deps-1, that promotes P-granule assembly and RNAi in C. elegans germ cells. They show that DEPS-1, a P-granule-associated protein, is required for several cellular events, including the expression of the granule-associated RNA helicase GLH-1, the constitutive association of PGL-1 (an RNA-binding protein) with P-granules and germ cell proliferation at elevated temperatures. In addition, DEPS-1 promotes the expression of RDE-4,an RNA-binding protein required for RNAi, and represses the expression of genes that are also regulated by the RNAi factor RDE-3. The researchers propose, therefore, that DEPS-1 is involved in some of the RNA regulatory functions of P granules, possibly by helping to generate small interfering RNAs.
