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Catalytic domain of the Dual-specificity protein kinase, Lymphokine-activated killer T-cell-originated protein kinase Dual-specificity PKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine as well as tyrosine residues on protein substrates. TOPK, also called PDZ-binding kinase (PBK), is activated at the early stage of mitosis and plays a critical role in cytokinesis. It partly functions as a mitogen-activated protein kinase (MAPK) kinase and is capable of phosphorylating p38, JNK1, and ERK2. TOPK also plays a role in DNA damage sensing and repair through its phosphorylation of histone H2AX. It contributes to cancer development and progression by downregulating the function of tumor suppressor p53 and reducing cell-cycle regulatory proteins. TOPK is found highly expressed in breast and skin cancer cells. The TOPK subfamily is part of a larger superfamily that includes the catalytic domains of other protein kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
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