Factor-dependent archaeal transcription termination.

RNA polymerase activity is regulated by nascent RNA sequences, DNA template sequences, and conserved transcription factors. Transcription factors promoting initiation and elongation have been characterized in each domain, but transcription termination factors have been identified only in bacteria and eukarya. Here we describe euryarchaeal termination activity (Eta), the first archaeal termination factor capable of disrupting the transcription elongation complex (TEC), detail the rate of and requirements for Eta-mediated transcription termination, and describe a role for Eta in transcription termination in vivo. Eta-mediated transcription termination is energy-dependent, requires upstream DNA sequences, and disrupts TECs to release the nascent RNA to solution. Deletion of TK0566 (encoding Eta) is possible, but results in slow growth and renders cells sensitive to DNA damaging agents. Our results suggest that the mechanisms used by termination factors in archaea, eukarya, and bacteria to disrupt the TEC may be conserved, and that Eta stimulates release of stalled or arrested TECs.