Glucose starvation induces a drastic reduction in the rates of both transcription and degradation of mRNA in yeast

Abstract

Gradual depletion of essential nutrients in yeast cultures induces a complex physiological response, leading initially to induction of pathways required for the utilization of alternative nutrients and, when such sources are depleted, to entry into stationary phase. Abrupt removal of sugar does not allow the proper establishment of stationary phase. Here we report that abrupt removal of glucose from the growth medium elicits a coordinated response in yeast cells that resembles, in some aspects, the gradual passage to stationary phase. Phosphorylation of RNA polymerase II at a subset of sites in the COOH-terminal domain (CTD) is decreased. Transcription by RNA polymerases I and II is shut down almost completely, whereas transcription by RNA polymerase III continues. In parallel, the rate of mRNA degradation is drastically reduced, at a stage preceding poly(A) shortening. This response is suited for conservation of scarce resources while preserving the ability of cells to recover when nutrients become available.