Function
Gamma subunit of the CTDK-I complex, which hyperphosphorylates the C-terminal heptapeptide repeat domain (CTD) of the largest RNA polymerase II subunit. CTDK-I phosphorylates 'Ser-5' if the CTD substrate is not phosphorylated at 'Ser-5', but will phosphorylate 'Ser-2' of a CTD substrate if 'Ser-5' is already phosphorylated. CTDK-I is also more reactive toward substrates that are prephosphorylated at 'Ser-2' or 'Ser-5' compared with an unphosphorylated CTD substrate, therefore efficiently creating doubly phosphorylated CTD repeats. Involved in RNA polymerase I transcription and RNA polymerase II transcriptional elongation, and as part of the CTDK-I complex, pre-mRNA 3'-end processing and SET2 mediated H3K36 methylation. Together with CTK2, required for CTK1 CTD kinase activation. Required for DNA damage induced transcription. Involved in the adaptation to alternative carbon sources, including galactose, glycerol and ethanol, but not raffinose. Required for the integrity of the rDNA locus.