Mapping of the interaction sites between Wee1 kinase and the regulatory beta-subunit of protein kinase CK2.

Somatic Wee1 is a protein kinase that plays a key role in cell cycle progression at the onset of mitosis by phosphorylating CDK1 at the inhibitory Tyr15 amino acid residue. Wee1 is regulated at multiple levels, i.e., phosphorylation, protein-protein association and proteasome-mediated degradation. We have recently shown that the regulatory beta-subunit of protein kinase CK2 participates in PLK1-Wee1 complex formation interacting directly with Wee1 and thereby contributing to the regulation of G2-M cell cycle transition. Here, we show that Wee1 binds CK2beta via two domains comprising amino acids 59-71 and 232-332. By employing deletion mutants of the CK2beta-subunit we also show that two regions between residues 1-5 and 155-170 are necessary for binding Wee1. Furthermore, we demonstrate that the interaction between CK2beta and Wee1 does not modify the kinase activity of the latter, instead CK2beta directly upregulates CDK1 kinase activity by reversing the inhibitory effect which follows Wee1-mediated phosphorylation. Taken together, our findings reinforce the notion that CK2beta is a modulator of protein kinases implicated in cell cycle regulation and exerts functions that are independent of CK2 tetramers.