UV-induced translation capacity is regulated developmentally in fungi

In fast-growing cells, most RNA molecules encode ribosomal subunits. During growth arrest caused by DNA damage, ribosome biogenesis is reduced because it is a highly energy-demanding process. Here, we report that, in two filamentous fungi, UV radiation significantly induces ribosome levels and translation capacity. This UV-induced response is developmentally regulated and occurs after filament formation. Translation induction modestly but significantly enhances both UV survival and repair. While some of the mRNAs that are differentially associated with ribosomes following UV exposure are associated with DNA repair, most of them belong to modules involved in protein folding and gene expression. TOR signaling is required for the immediate UV induction of ribosome biogenesis genes. However, we provide evidence that UV induces mechanisms that operate either upstream of or in parallel with TOR. These findings suggest a novel type of response to DNA damage, in which the primary aim is to protect the integrity of gene expression from the detrimental effects of UV radiation on transcription.