CDK13 (cyclin dependent kinase 13) is a transcriptional regulatory kinase that phosphorylates the C-terminal domain (CTD) of RNA polymerase II, playing crucial roles in gene expression and RNA processing 1. As a CTD kinase functioning in complex with cyclin K, CDK13 regulates transcription elongation and RNA splicing, though it exhibits distinct functions from the related CDK12 1. CDK13 is essential for nuclear RNA surveillance pathways, where it phosphorylates ZC3H14 to promote degradation of defective transcripts, preventing accumulation of aberrant RNAs 2. The kinase also regulates lipid metabolism in prostate cancer by interacting with NSUN5 to enhance m5C modification of ACC1 mRNA, promoting fatty acid synthesis and lipid accumulation 3. Disease-wise, CDK13 mutations are associated with neurodevelopmental disorders, with the gene showing female-biased enrichment in de novo mutations 4. In cancer contexts, CDK13 mutations contribute to melanoma development through disrupted RNA surveillance 2, while therapeutic targeting of CDK13 (along with CDK12) shows promise in triple-negative breast cancer by inducing DNA damage response deficiencies 5. These findings establish CDK13 as a multifunctional kinase critical for proper gene expression, RNA quality control, and cellular metabolism.