Fission yeast Puf2, a Pumilio and FBF family of RNA-binding protein, links stress granules to processing bodies.

Stress granules (SGs) are cytoplasmic aggregates formed upon stress when untranslated messenger ribonucleoproteins accumulate in the cells. In a GFP-library screening of the fission yeast SG proteins, Puf2 of the PUF family of RNA-binding proteins was identified that is required for SG formation after deprivation of glucose. Accordingly, puf2 mutant is defective in recovery from glucose starvation with a much longer lag to re-enter the cell cycle. In keeping with these results, Puf2 contains several low-complexity and intrinsically disordered protein regions with a tendency to form aggregates and, when over-expressed, represses translation to induce aggregation of poly(A) binding protein Pabp, the signature constituent of SGs. Intriguingly, over-expression of Puf2 also enhances the structure of processing bodies (PBs), another type of cytoplasmic RNA granules, a complex of factors involved in mRNA degradation. We demonstrate, in this study, a function of the fission yeast PB in SG formation and Puf2 may provide the link of these two structures.