An example of nucleotide excision repair. UVR proteins remove UV-induced damage from DNA strands

UV-damaged DNA 5' ‘ , . \TT \ V 3, 3. lllllll‘» IIV'lI‘» lll’ illlllll» ll" 5' 3! complex «UVR c 5’ 5’ cut 3’ cut DNA helicase “ UVR D mfif Damaged strand segment DNA polymerase DNA and DNA ligase polymerase 5' —> 3’ DNA synthesis 0 UVR AB complex binds opposite a thymine dimer. 9 UVR B dena- tures the DNA around the lesion. . 3'6 UVR A departs; UVR C binds and catalyzes 3’ and 5’ cuts. 0 DNA helicase UVR D helps release the damaged single strand; DNA polymerase and DNA ligase fill and seal the single-stranded gap. The lesion has been removed and the DNA duplex has been restored.