Repair of mitomycin C mono- and interstrand cross-linked DNA adducts by UvrABC: a new model

• Published in: Nucleic acids research 2010-11, Vol.38 (20), p.6976-6984
• Main Authors: Weng, Mao-wen, Zheng, Yi, Jasti, Vijay P, Champeil, Elise, Tomasz, Maria, Wang, Yinsheng, Basu, Ashis K, Tang, Moon-shong
• Format: Article
• Language: English
• Subjects: DNA Adducts - chemistry; DNA Adducts - metabolism; DNA Breaks, Double-Stranded; DNA Repair; Endodeoxyribonucleases - metabolism; Escherichia coli; Escherichia coli Proteins - metabolism; Genome Integrity, Repair and; Mitomycin - chemistry; Mitomycin - metabolism; Models, Genetic
• ISSN: 0305-1048; 1362-4962; 1362-4962
• DOI: 10.1093/nar/gkq576

Mitomycin C induces both MC-mono-dG and cross-linked dG-adducts in vivo. Interstrand cross-linked (ICL) dG-MC-dG-DNA adducts can prevent strand separation. In Escherichia coli cells, UvrABC repairs ICL lesions that cause DNA bending. The mechanisms and consequences of NER of ICL dG-MC-dG lesions that do not induce DNA bending remain unclear. Using DNA fragments containing a MC-mono-dG or an ICL dG-MC-dG adduct, we found (i) UvrABC incises only at the strand containing MC-mono-dG adducts; (ii) UvrABC makes three types of incisions on an ICL dG-MC-dG adduct: type 1, a single 5' incision on 1 strand and a 3' incision on the other; type 2, dual incisions on 1 strand and a single incision on the other; and type 3, dual incisions on both strands; and (iii) the cutting kinetics of type 3 is significantly faster than type 1 and type 2, and all of 3 types of cutting result in producing DSB. We found that UvrA, UvrA + UvrB and UvrA + UvrB + UvrC bind to MC-modified DNA specifically, and we did not detect any UvrB- and UvrB + UvrC-DNA complexes. Our findings challenge the current UvrABC incision model. We propose that DSBs resulted from NER of ICL dG-MC-dG adducts contribute to MC antitumor activity and mutations.