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 p. 983, 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.
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