MAP kinase-interacting kinases 1 (MNK1; EC 126.96.36.199) and MNK2, two related MAP kinase-activated protein kinases that are able to integrate signals emanating from both MAP kinase pathways and to phosphorylate eIF4E, were identified recently. Both MNK1 and MNK2 bind tightly to the growth factor-regulated MAP kinases, Erk1 and Erk2, and MNK1, but not Mnk2, also binds strongly to the stress-activated kinase, p38. Since MNK1 was found to be a member of the eIF4F complex by binding to the molecular scaffolding protein eIF4G, it represents a likely candidate to be the biological relevant kinase for the cap-binding eukaryotic initiation factor 4E in mitogen- and stress-induced cells.
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