文摘
Immediate-early response gene c-fos expression is repressed and not activated after serum stimulation of serum-starved fibroblasts transformed with E1A and cHA-ras oncogenes. We found previously that stress factors, such as anisomycin, activated c-fos gene transcription in E1A+ras transformants. The MEK/ERK signal pathway played a primary role in this activation. In this paper, we investigated the role of MKP-1-dependent regulation of the c-fos gene through dephosphorylation of ERK kinases. It was revealed that anisomycin activated MKP-1 transcription in E1A+ras transformants for no longer than 1 h and then the transcriptional level dropped. Using MAP-kinase inhibitors, it was established that MKP-1 transcription depended on MEK/ERK and JNK kinase rather than p38 cascades. The anisomycin-induced c-fos gene transcription is stronger after the cell transfection with siRNA MKP-1. Thus, the MKP-1 protein phosphatase carries out negative regulation of c-fos gene transcription by dephosphorylation of ERK kinases, which are key signal components in E1A+ras-transformed cells exposed to the stress agent anisomycin.