Analysis of RNA associated with P granules in germ cells of C-elegans adults

P granules are cytoplasmic structures of unknown function that are associat ed with germ nuclei in the C. elegans gonad, and are localized exclusively to germ cells, or germ cell precursors, throughout the life cycle. All the known protein components of P granules contain putative RNA-binding motifs, suggesting that RNA is involved in either the structure or function of the granules. However, no specific mRNAs have been identified within P granule s in the gonad. We show here that P granules normally contain a low level o f RNA, and describe conditions that increase this level. We present evidenc e that several, diverse mRNAs, including pos-1, mex-1, par-3, skn-1, nos-2 and gld-1 mRNA, are present at least transiently within P granules. In cont rast, actin and tubulin mRNA and rRNA are either not present in P granules, or are present at relatively low levels. We show that pgl-1 and the glh (V asa-related) gene family, which encode protein components of P granules, do not appear essential for RNA to concentrate in P granules; these proteins may instead function in events that are a prerequisite for RNAs to be trans ported efficiently from the nuclear surface.