P bodies, stress granules, and viral life cycles

Abstract

Eukaryotic mRNAs are in a dynamic equilibrium between different subcellular locations. Translating mRNAs can be found in polysomes, mRNAs stalled in translation initiation accumulate in stress granules and mRNAs targeted for degradation or translation repression can accumulate in P bodies. Partitioning of mRNAs between polysomes, stress granules, and P bodies affects rates of translation and mRNA degradation. Host proteins within P bodies and stress granules can enhance or limit viral infection, and some viral RNAs and proteins accumulate in P bodies and/or stress granules. Thus, an important interplay among P bodies, stress granules, and viral life cycles is beginning to emerge.

Figure 1. Cytoplasmic cycling of mRNA

mRNA in the cytoplasm of eukaryotic cells may either engage in translation or be sequestered into translationally repressed mRNPs. Stress granules in mammals are formed during various cellular stresses and include mRNA, translation initiation factors and TIA-R proteins. Alternatively, mRNA can be sequestered into P-bodies where the mRNA is stored for future use in translation, or decapped and degraded.