P38 RK IS ESSENTIAL FOR STRESS-INDUCED NUCLEAR RESPONSES - JNK/SAPKS AND C-JUN/ATF-2 PHOSPHORYLATION ARE INSUFFICIENT/

The ERK JNK/SAPK and p38/RK MAP kinase subtypes (reviewed in [1]) are differentially activated in mammalian cells by various stimuli, which elicit induction of immediate-early (IE) genes, such as c-fos and c-ju n (reviewed in [1-3]), as well as phosphorylation of histone H3 [4] an d HMG-14 [5]. Anisomycin and UV radiation have been suggested to induc e c-fos and c-jun transcription via JNK/SAPK-mediated phosphorylation of TCF (ternary complex factor), for c-fos induction [6-8], and c-Jun and/or ATF-2 for c-jun induction [9-13]. We report here that anisomyci n and ultraviolet radiation (UV) activate MAP kinase kinase-6 (MKK6) [ 14,15], p38/RK [16-18] and MAPKAP kinase-2 (MAPKAP K-2) [17-19]. By us ing the p38/RK inhibitor SE 203580 [20,21], we show that activation of p38/RK and/or its downstream effecters are essential for anisomycin a nd UV-stimulated c-fos/c-jun induction and histone H3/HMG-14 phosphory lation, whereas JNK/SAPK activation and phosphorylation of c-Jun and A TF-2 are insufficient for these responses.