title: Early steps of excision repair of cyclobutane pyrimidine dimers by the Micrococcus luteus endonuclease. A three-step incision model.
abstract: The early steps of excision repair of cyclobutane pyrimidine dimers are investigated. It is demonstrated that the apurinic/apyrimidinic endonuclease associated with the Micrococcus luteus uv-specific endonuclease cleaves the phosphodiester bond on the 3' side of the deoxyribose leaving a 3' hydroxy terminus and a 5' phosphoryl terminus. This nick is not a substrate for T4 polynucleotide ligase. The 3' base-free deoxyribose terminus is not a substrate for either the polymerase or the 3' to 5' exonuclease activities of Escherichia coli DNA polymerase I. However, the 3' terminus of the nick is converted to a substrate for DNA polymerization by the action of a 5' apurinic/apyrimidinic endonuclease. A three-step model for the incision step of excision repair of cyclobutane pyrimidine dimers is presented.
mesh_terms: D000469:Alkaline Phosphatase; D001483:Base Sequence; D003503:Cyclobutanes / Q000378:metabolism*; D004260:DNA Repair; D043224:Deoxyribonuclease (Pyrimidine Dimer); D003851:Deoxyribonucleases / Q000378:metabolism*; D004720:Endonucleases / Q000378:metabolism*; D005260:Female; D006801:Humans; D008837:Micrococcus / Q000201:enzymology*; D010920:Placenta / Q000201:enzymology; D011247:Pregnancy; D011740:Pyrimidine Dimers / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D003503:Cyclobutanes; D011740:Pyrimidine Dimers; D003851:Deoxyribonucleases; D004720:Endonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); D000469:Alkaline Phosphatase