 MKK3 and SEK activate p38 MAP kinase by phosphorylation at Thr-180 and Tyr-182.Activated p38 MAP kinase has been shown to phosphorylate and activate MAPKAP kinase 2 and to phosphorylate the transcription factors ATF2, Mac and MEF2.p38 also has been shown to phosphorylate post-transcriptional regulating factors like TTP.