PBK (PDZ binding kinase) belongs to the serine/threonine protein kinase family. It is related to the dual specific mitogen-activated protein kinase kinase (MAPKK) family and phosphorylates MAP kinase p38. It is active only in mitosis. When phosphorylated it forms a complex with TP53, leading to TP53 destabilization and attenuation of G2/M checkpoint during doxorubicin-induced DNA damage. It makes a kinase-substrate complex with cdk1/cyclin B1 and PRC1 on microtubules during mitosis, enhances the cdk1/cyclin B1-dependent phosphorylation of PRC1 and thereby strongly promotes cytokinesis. It may play a role in the activation of lymphoid cells.