Abortive ligation during base excision repair (BER) leads to blocked repair intermediates containing a 5'-adenylated-deoxyribose phosphate (5'-AMP-dRP) group. Aprataxin (APTX) is able to remove the AMP group allowing repair to proceed. Earlier results had indicated that purified DNA polymerase β (pol β) removes the entire 5'-AMP-dRP group through its lyase activity and flap endonuclease 1 (FEN1) excises the 5'-AMP-dRP group along with one or two nucleotides. Here, using cell extracts from APTX-deficient cell lines, human Ataxia with Oculomotor Apraxia Type 1 (AOA1) and DT40 chicken B cell, we found that pol β and FEN1 enzymatic activities were prominent and strong enough to complement APTX deficiency. In addition, pol β, APTX and FEN1 coordinate with each other in processing of the 5'-adenylated dRP-containing BER intermediate. Finally, other DNA polymerases and a repair factor with dRP lyase activity (pol λ, pol ι, pol θ and Ku70) were found to remove the 5'-adenylated-dRP group from the BER intermediate. However, the activities of these enzymes were weak compared with those of pol β and FEN1.
Published by Oxford University Press on behalf of Nucleic Acids Research 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.