Human transcription-repair coupling factor CSB/ERCC6 is a DNA-stimulated ATPase but is not a helicase and does not disrupt the ternary transcription complex of stalled RNA polymerase II.
Transcription is coupled to repair in Escherichia coli and in humans. Proteins encoded by the mfd gene in E. coli and by the ERCC6/CSB gene in humans, both of which possess the so-called helicase motifs, are required for the coupling reaction. It has been shown that the Mfd protein is an ATPase but not a helicase and accomplishes coupling, in part, by disrupting the ternary complex of E. coli RNA polymerase stalled at the site of DNA damage. In this study we overproduced the human CSB protein using the baculovirus vector and purified and characterized the recombinant protein. CSB has an ATPase activity that is stimulated strongly by DNA; however, it neither acts as a helicase nor does it dissociate stalled RNA polymerase II, suggesting a coupling mechanism in humans different from that in prokaryotes. CSB is a DNA-binding protein, and it also binds to XPA, TFIIH, and the p34 subunit of TFIIE. These interactions are likely to play a role in recruiting repair proteins to ternary complexes formed at damage sites.
Selby
C P
CP
Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA.
Sancar
A
A
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D004265:DNA Helicases / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004789:Enzyme Activation; D006801:Humans; D000075223:Poly-ADP-Ribose Binding Proteins; D012319:RNA Polymerase II / Q000378:metabolism; D014158:Transcription, Genetic
D000075223:Poly-ADP-Ribose Binding Proteins; D004247:DNA; D012319:RNA Polymerase II; D000251:Adenosine Triphosphatases; D004265:DNA Helicases; C078673:ERCC6 protein, human; D045643:DNA Repair Enzymes