Osmostress-induced gene expression--a model to understand how stress-activated protein kinases (SAPKs) regulate transcription

Abstract

Adaptation is essential for maximizing cell survival and for cell fitness in response to sudden changes in the environment. Several aspects of cell physiology change during adaptation. Major changes in gene expression are associated with cell exposure to environmental changes, and several aspects of mRNA biogenesis appear to be targeted by signaling pathways upon stress. Exhaustive reviews have been written regarding adaptation to stress and regulation of gene expression. In this review, using osmostress in yeast as a prototypical case study, we highlight those aspects of regulation of gene induction that are general to various environmental stresses as well as mechanistic aspects that are potentially conserved from yeast to mammals.

Keywords: Hog1; SAPK; gene expression; mammals; osmostress; p38; stress responses; yeast.

Figure 1

Stress‐induced gene expression by Hog1. (A) Schematic graph of bimodal expression of a fluorescent osmoresponsive reporter under low (0.1 m NaCl), high (0.4 m NaCl) and non‐osmostress conditions, measured by single‐cell flow cytometry. (B) Control of stress‐responsive mRNA biogenesis by the Hog1 SAPK. Once activated, Hog1 associates with stress‐responsive loci to modulate chromatin remodeling and histone modifications, transcriptional initiation and elongation. Hog1 also participates in mRNA processing, mRNA export and translation. (C) The Hog1 SAPK coordinates transcription with DNA replication. Upon osmostress, the activated Hog1 activates transcription and delays DNA replication by phosphorylating Mrc1. This coordinated regulation of the two processes prevents collisions between transcription and replication machineries and protects genomic integrity.