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

Gradual depletion of essential nutrients in yeast cultures induces a comple x physiological response, leading initially to induction of pathways requir ed 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 abr upt removal of glucose from the growth medium elicits a coordinated respons e in yeast cells that resembles, in some aspects, the gradual passage to st ationary phase. Phosphorylation of RNA polymerase II at a subset of sites i n the COOH-terminal domain (CTD) is decreased. Transcription by RNA polymer ases I and II is shut down almost completely, whereas transcription by RNA polymerase III continues. In parallel, the rate of mRNA degradation is dras tically 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. (C) 2000 Elsevier Scienc e B.V. All rights reserved.