transcription elongation factor complex cyclin/CDK positive transcription elongation factor complex cellular_component positive transcription elongation factor complex b GO:0008024 See also the cellular component terms 'cyclin-dependent protein kinase activating kinase holoenzyme complex ; GO:0019907' and 'DNA-directed RNA polymerase II, holoenzyme ; GO:0016591'. A transcription elongation factor complex that facilitates the transition from abortive to productive elongation by phosphorylating the CTD domain of the large subunit of DNA-directed RNA polymerase II, holoenzyme. Contains a cyclin and a cyclin-dependent protein kinase catalytic subunit. nuclear cyclin-dependent protein kinase holoenzyme complex carboxy-terminal domain protein kinase complex