RNA granules: post-transcriptional and epigenetic modulators of gene expression

Compositionally and functionally distinct RNA granules are found in the cytoplasm of somatic and germ cells. The components of most RNA granules are in a dynamic equilibrium, thereby allowing rapid shifts between the translation, storage and decay of RNAs. The composition of cytoplasmic messenger ribonucleoproteins (mRNPs) is determined by their nuclear and cytoplasmic histories and reflects past functions and future fates. The protein components of selected mRNP complexes promote their assembly into microscopically visible cytoplasmic RNA granules, including stress granules, processing bodies and germ cell (or polar) granules. We propose that RNA granules can be both a cause and a consequence of altered mRNA translation, decay or editing. In this capacity, RNA granules serve as key modulators of post-transcriptional and epigenetic gene expression.