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Strand opening by the UvrA(2)B complex allows dynamic recognition of DNA damage
1Sealy Center for Molecular Science, Department of Human Biological Chemistry, University of Texas Medical Branch, Galveston, TX 77555, USA.
The EMBO Journal
|September 2, 1999
Summary
DNA repair proteins use DNA melting to recognize and process damage. Escherichia coli UvrBC endonuclease incises DNA at specific bubble structures, revealing conserved mechanisms in nucleotide excision repair (NER).
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Nucleotide excision repair (NER) involves proteins that alter DNA structure.
- The exact role of DNA melting in NER is not fully understood.
Purpose of the Study:
- To investigate the role of DNA melting and bubble structures in DNA damage recognition and incision by Escherichia coli UvrBC endonuclease.
- To determine how DNA structure influences the formation of repair intermediates and the incision steps in NER.
Main Methods:
- Utilized site-specific BPDE-guanine adducts within DNA substrates containing non-complementary base regions.
- Examined incision activity of UvrBC endonuclease, with and without UvrA, on various DNA bubble structures.
- Analyzed stable repair intermediates formed by UvrB or UvrBC.
Main Results:
- UvrBC formed a pre-incision intermediate with a 6-base DNA bubble structure.
- The distance between the adduct and the double-stranded-single-stranded DNA junction of the bubble determined dual incision efficiency.
- UvrBC performed dual incisions on bubbles of 3-6 nucleotides and a 5' incision on larger bubbles (>10 nucleotides) even without UvrA.
Conclusions:
- DNA bubble formation is a dynamic recognition step in DNA damage processing during NER.
- The incision activity of UvrBC is dependent on bubble size and proximity to DNA junctions.
- E. coli and human NER systems exhibit conserved mechanisms for DNA damage recognition and processing.