Open AccessDNA binding activity from cultured human fibrolasts that is specific for partially depurinated DNA and that inserts purines into apurinic sites.
Author(s) -
Walter Deutsch,
Stuart Linn
Publication year - 1979
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.76.1.141
Subject(s) - ap site , guanine , dna , purine , biochemistry , pyrimidine , base excision repair , ap endonuclease , nucleobase , chemistry , cytosine , depurination , nucleotide , dna repair , dna glycosylase , divalent , microbiology and biotechnology , enzyme , biology , gene , organic chemistry
A protein of molecular weight approximately 120,000 was isolated from cultured human fibroblasts and HeLa cells on the basis of its ability to bind specifically to apurinic DNA. After separation from apurinic endonuclease activity, the protein was found to incorporate purine, but not pyrimidine, bases specifically into depurinated DNA so as to protect the apurinic sites from alkali. Purine base insertion activity was sensitive to heating and freezing as well as to caffeine and EDTA; it required K+ but not a divalent cation. Guanine, but not adenine, was incorporated into depurinated poly(dG-dC), whereas adenine, but not guanine, was incorporated into poly(dA-dT). After incorporation into depurinated DNA, guanine could be reisolated as dGMP. Although this activity suggests an alternative pathway for DNA repair that is independent of nucleotide excision, other functions for such an enzyme are possible.