Enables protein kinase binding activity. Acts upstream of or within negative regulation of stem cell differentiation. Predicted to be located in nuclear speck. Predicted to be part of cyclin K-CDK12 complex and cyclin/CDK positive transcription elongation factor complex. Predicted to be active in nucleus. Is expressed in several structures, including blastocyst; early embryo; future brain; primitive streak; and unsegmented mesenchyme. Orthologous to human CDK12 (cyclin dependent kinase 12). [provided by Alliance of Genome Resources, Apr 2022]