Mechanism of Action of M. luteus Apurinic/Apyrimidinic Endonucleases
Apurinic/apyrimidinic sites (AP-sites) occur in DNA. They could have different origin : spontaneous depurination, excision by specific DNA glycosylases of damaged bases. Such lesions are repaired by two independant mechanisms1.In the repair by reinsertion, specific insertase inserts the missing purine and regenerates the integrity of DNA. In the repair by base excision, a specific endonuclease for AP-sites (AP-endonuclease) recognises the lesion and incises the DNA backbone near the lesion. The termini generated by AP-endonucleases are of importance as they determine the polarity of the excision of the lesion. Furthermore there is an increasing interest for AP-endonucleases since pyrimidine dimers are excised in M. luteus by base excision2. In this paper we report the determination of the termini generated by the two different AP-endonucleases extracted from M. luteus. We also report experiments showing that these enzymes could be used to detect AP-sites introduced in DNA by γ-rays or by UV irradiation.
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