Thermosensitivity of cellular translation restricts the growth of fission yeast at high temperatures

Living organisms have thermal limits above which they are unable to operate and survive. Our previous genetic screen identified proteins that impede the high-temperature growth of fission yeast, including the RNA-binding protein Dri1 and a fission yeast-specific protein termed Rhs1. Here, we show that Dri1 and Rhs1 form a complex and physically interact with the Ccr4-Not complex, a master regulator of mRNA metabolism. Gene expression analysis revealed that the Dri1-Rhs1 and Ccr4-Not complexes negatively regulate a set of genes implicated in ribosome biogenesis (Ribi genes). Loss of the Dri1-Rhs1 complex results in the augmented expression of Ribi genes, thereby suppressing the accumulation of 80S monosomes and the growth inhibition under high-temperature conditions. The thermosensitivity of the translational processes may be a determinant of the upper limit of the growth temperature in fission yeast.