title: Human AP endonuclease possesses a significant activity as major 3'-5' exonuclease in human leukemia cells.
abstract: Apurinic/apyrimidinic (AP) endonuclease (Ape1) is the major cellular enzyme responsible for repairing AP-sites in DNA. It can cleave the DNA phosphodiester backbone immediately 5(') to an AP-site. Ape1 also shows 3(')-phosphodiesterase activity, a 3(')-phosphatase activity, and an RNaseH activity. However, regarding its exonuclease activity, it remains controversial whether human Ape1 may possess a 3(')-5(') exonuclease activity. During the course of study to search for the major nuclease activity to double-stranded DNA in human leukemia cells, we purified a 37 kDa Mg(2+)-dependent exonuclease from cytosolic fraction of human leukemia U937 cells. Surprisingly, this exonuclease is Ape1. We demonstrated for the first time that Ape1 possesses a significant activity as major 3(')-5(') exonuclease in human leukemia cells. In addition, we also observed that translocation of cytoplasmic Ape1 into nucleus occurs during DNA damage.
authors.affiliation: First Department of Internal Medicine, Fukui Medical University, Matsuoka-cho, Fukui 910-1193, Japan. yoshida99@mac.com
authors.forename: Akira
authors.initials: A
authors.lastname: Yoshida
authors.forename: Takanori
authors.initials: T
authors.lastname: Ueda
mesh_terms: D002467:Cell Nucleus / Q000201:enzymology; D003593:Cytoplasm / Q000201:enzymology; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000032:analysis / Q000378:metabolism*; D005090:Exodeoxyribonucleases / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D007938:Leukemia / Q000201:enzymology*; D020298:U937 Cells
chemical_list: D005090:Exodeoxyribonucleases; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase