Essential for appropriate transcription during embryonic development. May act during transcription elongation to activate the RNA polymerase II large subunit (ama-1) by phosphorylating the Ser-2 residues of the C-terminal domain 7-residue repeats. Does not phosphorylate histone H3. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with air-2. Expressed in embryos from the 2-cell stage until morphogenesis. May also be maternally expressed. Not expressed during mitosis. Autophosphorylates in vitro. Phosphorylation on Ser-634 by air-2 enhances catalytic activity. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.