Catalytic domain of Cyclin-Dependent protein Kinase 8-like Serine/Threonine Kinases
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. This subfamily is composed of CDK8, CDC2L6, and similar proteins. CDK8 functions as a negative or positive regulator of transcription, depending on the scenario. Together with its regulator, cyclin C, it reversibly associates with the multi-subunit core Mediator complex, a cofactor that is involved in regulating RNA polymerase II-dependent transcription. CDC2L6 also associates with Mediator in complexes lacking CDK8. In VP16-dependent transcriptional activation, CDK8 and CDC2L6 exerts opposing effects by positive and negative regulation, respectively, in similar conditions. CDKs belong to a large family of STKs that are regulated by their cognate cyclins. Together, they are involved in the control of cell-cycle progression, transcription, and neuronal function. The CDK8-like subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
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