CDK12 and CDK13 are C-terminal domain (CTD) serine kinases that phosphorylate Ser2 in the CTD of RNA polymerase II and which regulate co-transcriptional processing, including splicing and 3'-end RNA processing [1,3-5]. Although CDK12 and CDK13 are closely related structurally, they differ in function. Whilst CDK12 is essential for the expression of genes that are involved in the DNA damage response pathway [2] (generally longer genes with a high number of exons), CDK13 activity affects genes that are required for protein translation.

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3. Davidson L, Muniz L, West S. (2014) 3' end formation of pre-mRNA and phosphorylation of Ser2 on the RNA polymerase II CTD are reciprocally coupled in human cells. Genes Dev, 28 (4): 342-56. [PMID:24478330]

4. Eifler TT, Shao W, Bartholomeeusen K, Fujinaga K, Jäger S, Johnson JR, Luo Z, Krogan NJ, Peterlin BM. (2015) Cyclin-dependent kinase 12 increases 3' end processing of growth factor-induced c-FOS transcripts. Mol Cell Biol, 35 (2): 468-78. [PMID:25384976]

5. Kohoutek J, Blazek D. (2012) Cyclin K goes with Cdk12 and Cdk13. Cell Div, 7: 12. [PMID:22512864]