... Chinese hamster apurinic⁄apyrimidinic endonuclease (chAPE1) expressed in sf9 cells reveals that its endonuclease activity is regulated by phosphorylation Mandula Borjigin1, Bobbie Martinez2, ... pathway by creating a nick 5¢ toan abasic site in double-stranded DNA. Although the Chinese hamster ovary cells remain an important model for DNA repair studies, the Chinese hamster APE (chAPE1) ... expression. The recombinant chAPE1has 44 potential phosphorylation sites (serine, threonine, tyrosine).The protein contains 11 sulfur atoms (in methionine, cystine), and its molecular mass is 35.5 kDa....