Human apurinic/apyrimidinic endonuclease 1 (APE1) is a key DNA repair enzyme
involved in both base excision repair (BER) and nucleotide incision repair (NIR) pathways. In the BER
pathway, APE1 cleaves DNA at AP sites and 3'-blocking moieties generated by DNA glycosylases. In the
NIR pathway, APE1 incises DNA 5' to a number of oxidatively damaged bases. Here we propose to identify
and characterize critical amino acids of APE1 involved in either BER and/or NIR functions by using
the alignment of the known three-dimensional (or tertiary) structures of Xth family AP endonucleases
including the Methanothermobacter thermautotrophicus Mth212, Bacillus subtilis ExoA (1), E. coli Xth
and human APE1 proteins (2)
