MAPK pathways are well-studied regulatory elements linked to the regulation of nuclear gene expression by its interaction with transcription factors. An additional and equally interesting level of control of gene expression is provided by mechanisms that control mRNA stability. Our results indicate that while ERK2 promotes fos gene transcription, another MAPK (p38 MAPK) regulates fos mRNA decay by affecting the state of phosphorylation of specific mRNA binding proteins. In this fashion, concerted early (ERK) or late (p38) MAPK activation can contribute to both rapid and transient activation of the early responsive gene fos.