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Ape1- And Ape2-Dependent Dna Breaks In Immunoglobulin Class Switch Recombination, Jeroen E. J. Guikema, Erin K. Linehan, Daisuke Tsuchimoto, Yusaku Nakabeppu, Phyllis R. Strauss, Janet Stavnezer, Carol E. Schrader

Janet M. Stavnezer

Antibody class switch recombination (CSR) occurs by an intrachromosomal deletion requiring generation of double-stranded breaks (DSBs) in switch-region DNA. The initial steps in DSB formation have been elucidated, involving cytosine deamination by activation-induced cytidine deaminase and generation of abasic sites by uracil DNA glycosylase. However, it is not known how abasic sites are converted into single-stranded breaks and, subsequently, DSBs. Apurinic/apyrimidinic endonuclease (APE) efficiently nicks DNA at abasic sites, but it is unknown whether APE participates in CSR. We address the roles of the two major mammalian APEs, APE1 and APE2, in CSR. APE1 deficiency causes embryonic lethality in mice; …