Table 1.

Transcript Elongation, Proofreading and Repair by RNA Polymerases

	Polymerase Function	3′→5′ Nuclease Activity	References	Cleavage Induction	References
Archaeal DdRp	Transcription	✓	Hausner, Lange, and Musfeldt (2000)	TFS (homologous to eukaryotic TFIIS)	Hausner, Lange, and Musfeldt (2000), Lange and Hausner (2004)
Bacterial DdRp	Transcription	✓	Orlova et al. (1995)	GreA/GreB (functionally analogous to TFIIS)	Borukhov, Sagitov, and Goldfarb 1993, Erie et al. (1993)
Eukaryotic DdRp I	rRNA transcription	✓	Tschochner (1996)	TFIISa	Schnapp, Graveley, and Grummt (1996)
Eukaryotic DdRp II	mRNA and snRNA transcription	✓	Wang and Hawley (1993), Thomas, Platas, and Hawley (1998)	TFIIS	Jeon and Agarwal (1996)
Eukaryotic DdRp III	Transcription of tRNA, 5S rRNA, U6 snRNA, snoRNA	✓	Whitehall, Bardeleben, and Kassavetis (1994)	TFIIS	Chédin et al. (1998)
Vaccinia virus DdRp	Transcription and replication	✓	Hagler and Shuman (1993)	TFIIS role in proofreading unclear	Rosales et al. (1994)
T7 DNA phage DdRpb	Transcription	✓	Sastry and Ross (1997)	—	—
Influenza virus RdRpb	Transcription and replication	✓	Ishihama et al. (1986), Ishihama (1996)	—	—

NOTE.—Abbreviations: DdRp, DNA-dependent RNA polymerase; RdRp, RNA-dependent RNA polymerase; GreA/GreB, growth regulator A/B; TFIIS, transcription factor IIS; TFS, transcription factor S.

^aAlso known as SII.

^bSingle subunit RNA polymerases, evolutionarily unrelated to multisubunit RNA polymerases.