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Rodent UV-sensitive mutant cell lines in complementation groups 6-10 have normal general excision repair activity
J T Reardon1, L H Thompson, A Sancar
1Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7260, USA.
Nucleic Acids Research
|March 1, 1997
Summary
Mammalian nucleotide excision repair removes DNA damage via incision, excision, and gap filling. Rodent mutants defective in DNA repair show normal in vitro activity, suggesting defects lie outside this pathway.
Area of Science:
- Molecular Biology
- DNA Repair Mechanisms
- Biochemistry
Background:
- Nucleotide excision repair (NER) is crucial for removing bulky DNA lesions.
- NER involves dual incisions, excision of a DNA fragment, and gap filling.
- Understanding NER is vital for comprehending DNA stability and disease pathogenesis.
Purpose of the Study:
- To characterize the individual steps of mammalian nucleotide excision repair.
- To determine the precise incision sites and oligonucleotide length released during excision.
- To investigate the functional capacity of NER in specific rodent mutants.
Main Methods:
- Development of specific assays for incision, excision, and repair patch synthesis.
- Utilizing cell-free extracts from UV-sensitive rodent mutants.
- Employing the 'phosphorothioate repair patch assay' to identify DNA polymerases involved.
Main Results:
- Mammalian NER incises DNA at phosphodiester bonds flanking lesions, releasing oligonucleotides of 26-29 nucleotides.
- DNA polymerases delta and epsilon are responsible for filling the post-excision gap.
- Moderately UV-sensitive rodent mutants (complementation groups 6-10) exhibit normal in vitro NER activity.
Conclusions:
- The characterized mammalian NER pathway precisely removes bulky DNA lesions.
- The identified rodent mutants possess normal in vitro DNA repair capabilities.
- The genetic defects in these mutants likely affect cellular functions distinct from general NER.