CDK8 and CDK19 are incorporated in a mutually exclusive manner

CDK8 and CDK19 are two closely related cyclin-dependent kinases (CDKs) that have been shown to play important roles in various cellular processes, including transcriptional regulation and cell cycle control. Although these two CDKs share a high degree of sequence similarity and are often found together in protein complexes, recent studies have revealed that they are incorporated into these complexes in a mutually exclusive manner.

This means that when one of these CDKs is present in a protein complex, the other is not. For example, CDK8 is part of the Mediator complex, which is involved in transcriptional regulation, but CDK19 is not. Conversely, CDK19 is part of the p-TEFb complex, which is involved in RNA polymerase II elongation, but CDK8 is not.

The reason for this mutual exclusivity is not yet fully understood, but it may be due to differences in the binding partners and substrates of these two CDKs. By being incorporated into different complexes, CDK8 and CDK19 may be able to regulate distinct sets of genes and cellular processes, thereby contributing to the diversity and specificity of CDK signaling in cells