Fig. 1.

CK2 regulates ERK nuclear import. In the absence of growth-promoting signals, ERK mainly resides in the cytoplasm associated with MEK and other anchoring proteins. Growth signals stimulate the RAS-RAF-MEK pathway, leading to the phosphorylation of the ERK activation loop and its dissociation from the anchoring proteins. This allows CK2 to phosphorylate the ERK NTS, which provides a binding site for Imp7. The ERK-Imp7 complex is imported into the nucleus, where ERK targets its nuclear substrates, including transcriptional regulatory proteins.