Saccharomyces cerevisiae SFP1: at the crossroads of central metabolism and ribosome biogenesis.

Saccharomyces cerevisiae SFP1 is required for nutrient-dependent regulation of ribosome biogenesis and cell size. A mutant deleted for SFP1 shows specific traits, including a slow growth phenotype, especially when growing on glucose. We recently analysed the physiology of an sfp1Delta mutant and its isogenic reference strain in chemostat cultures. This approach was successful in revealing the effects of nutrients on the activity of Sfp1 independent of growth rate-related feedback. In the present work we exposed carbon-limited cultures of an sfp1Delta mutant and its reference strain to sudden glucose excess. This allowed us to study the effect of SFP1 deletion on cell physiology when the cells are forced to exploit their maximum growth potential; this is similar to what happens in shake-flask cultures but with no bias due to growth rate differences. We show that nutrients differentially affect the role of Sfp1 in cell-size modulation and in transcriptional control. Furthermore, we report that while Sfp1 is necessary for the efficient glucose-dependent regulation of ribosome biogenesis genes, it is not required for the proper induction of ribosomal protein genes in response to glucose excess. Finally, our data suggest a role for Sfp1 in the regulation of glycolysis, further underlining its involvement in the network that links ribosome biogenesis and cell metabolism.