Enables several functions, including RNA polymerase II CTD heptapeptide repeat kinase activity; chromatin binding activity; and nucleic acid binding activity. Involved in positive regulation of histone H2B ubiquitination and positive regulation of histone phosphorylation. Located in nucleus. Part of cyclin/CDK positive transcription elongation factor complex. Is expressed in several structures, including alimentary system; early embryo; genitourinary system; hemolymphoid system; and nervous system. Orthologous to human CDK9 (cyclin dependent kinase 9). [provided by Alliance of Genome Resources, Apr 2022]