3′-Phosphodiesterase activity of human apurinic/apyrimidinic endonuclease at DNA double-strand break ends

摘要: In order to assess the possible role of human apurinic/apyrimidinic endonuclease (Ape) in double-strand break repair, substrate specificity this enzyme was investigated using short DNA duplexes and partial duplexes, each having a single 3'-phosphoglycolate terminus. Phosphoglycolate removal by Ape detected as shift mobility 5'-end-labeled strands on polyacrylamide sequencing gels, quantified phosphorimaging. Recombinant efficiently removed phosphoglycolates from 3'-terminus an internal 1 base gap 38mer duplex, but acted more slowly 3'-phosphoglycolates at 19 base-recessed 3'-terminus, nick with no missing bases, end either blunt or 2 3'-termini. There detectable activity toward protruding single-stranded 3'-overhangs. The results suggest that both single-base gap, duplex side are important binding/recognition determinants for Ape. While may play repair terminally blocked breaks, there must also be additional factors involved least some damaged 3'-termini, particularly those