. Author manuscript; available in PMC: 2013 Dec 31.

Published in final edited form as: Cancer Lett. 2012 Feb 19;327(1-2):61–72. doi: 10.1016/j.canlet.2012.02.001

Table 3.

The major steps and protein participants in global genome and transcription-coupled NER. Only the recognition step differs between these two sub-pathways of NER.

NER STEP		PROTEIN	BIOCHEMICAL ACTIVITY	SUBSTRATE
RECOGNITION	GLOBAL GENOME	XPC/RAD23B	DNA Binding/TFIIH recruitment	DNA helix distortion
		DDB1/DDB2 (XPE)	DNA Binding	UV-damaged DNA
		XPA	DNA Binding	XPC-TFIIH bound DNA
	TRANSCRIPTION COUPLED	CSA	Unknown/Part of ubiquitin ligase complex	Stalled RNA Pol
	TRANSCRIPTION COUPLED	CSB	DNA-dependent ATPase	Stalled RNA Pol
DNA UNWINDING (TFIIH Multisubunit Complex^*)		XPB (ERCC3)	3′ to 5′ DNA helicase/ATPase
DNA UNWINDING (TFIIH Multisubunit Complex^*)		XPD (ERCC2)	5′ to 3′ DNA helicase/ATPase
INCISION		XPG (ERCC5)	3′-Incision	5′-Flap, Bubble
INCISION		ERCC1/XPF (ERCC4)	5′-Incision complex (catalyzed by XPF)	3′-Flap, Bubble
POLYMERIZATION		POLδ (POLε)	PCNA-dependent replicative polymerase(s)	DNA gap (~25–30 nt)
LIGATION		LIG1	Ligase	DNA nick
LIGATION		XRCC1/LIG3α	Ligase complex	DNA nick

Of the multiple subunits that comprise the TFIIH transcription complex, only XPB and XPD are listed here. RPA (not listed) participates in NER by binding and protecting the single-stranded DNA regions generated upon duplex unwinding.