Stress-activated MAP kinases in chromatin and transcriptional complexes

Stress-activated MAP kinases (SAPKs) are activated by stressors or by certain physiological stimuli and mediate an intracellular response appropriate to the change in environment. Long-term adaptation requires reprogramming of transcription and one of the most significant actions of SAPK cascades is therefore induction of gene expression. SAPKs and their downstream kinases phosphorylate many chromatin-associated and transcription factors. Further, they can induce localised histone modification by regulating histone acetyltransferases and deacetylases. p38/SAPK2 also elicits phosphorylation of the nucleosomal proteins histone H3 and HMGN1 (previously HMG-14) via the downstream mitogen- and stress-stimulated kinases MSK1/2. Finally, recent evidence indicates a novel non-enzymatic SAPK function in transcriptional complexes, suggesting a more structural role. The yeast SAPK Hog1p is recruited to a proportion of its target genes on activation and localises beyond the promoter into coding regions. The observation that Hog1p interacts with elongating RNA polymerase II in addition to several transcriptional elongation factors has led to the suggestion that this SAPK may behave like an elongation factor at some target genes. The generality of this new function is discussed. © 2007 Springer-Verlag Berlin Heidelberg.