Interaction between the noncatalytic region of Sid1p kinase and Cdc14p is required for full catalytic activity and localization of Sid1p

Sid1p is a group II p21-activated kinase/germinal center kinase family memb er that is part of a signaling network required for cytokinesis in fission yeast. Germinal center kinases are characterized by well conserved amino-te rminal catalytic domains followed by less conserved carboxyl termini. The c arboxyl termini among group I germinal center kinases are moderately conser ved and thought to be regulatory regions. Little is known about the carboxy l termini of group II family members. Sid1p has been shown to bind the nove l protein Cdc14p; however, the functional significance of this interaction is unknown. Here we report that the carboxyl terminus of Sid1p is an essent ial regulatory region. Our results indicate that this region contains the b inding domain for Cdc14p, and this association is required for full Sid1p c atalytic activity as well as intracellular localization. Furthermore, overe xpression of the carboxyl terminus of Sid1p alone compromises the signaling of cytokinesis. We conclude that Cdc14p positively regulates the Sid1p kin ase by binding the noncatalytic carboxyl-terminal region of the protein.