The roles of APE1, APE2, DNA polymerase beta and mismatch repair in creating S region DNA breaks during antibody class switch
Department of Molecular Genetics and Microbiology, Program in Immunology and Virology
*DNA Breaks; DNA Mismatch Repair; DNA Polymerase beta; DNA-(Apurinic or Apyrimidinic Site) Lyase; G1 Phase; Immunoglobulin Class Switching; Immunoglobulin Switch Region; Models, Genetic
Life Sciences | Medicine and Health Sciences
Immunoglobulin class switch recombination (CSR) occurs by an intrachromosomal deletion requiring generation of double-stranded DNA breaks (DSBs) in immunoglobulin switch region DNA. The initial steps of DSB formation have been elucidated: cytosine deamination by activation-induced cytidine deaminase (AID) and the generation of abasic sites by uracil-DNA glycosylase (UNG). We show that abasic sites are converted into single-strand breaks (SSBs) by apurinic/apyrimidinic endonucleases (APE1 and APE2). If SSBs are near to each other on opposite strands, they will generate DSBs; but if distal from each other, mismatch repair appears to be required to generate DSBs. The resulting S region DSBs occur at dC residues that are preferentially targeted by AID. We also investigate whether DNA polymerase beta, which correctly repairs SSBs resulting from APE activity, attempts to repair the breaks during CSR. We find that although polymerase beta does attempt to repair S region DNA breaks in switching B cells, the frequency of AID-instigated breaks appears to outnumber the SSBs repaired correctly by polymerase beta, and thus some DSBs and mutations are generated. We also show that the S region DSBs are introduced and resolved during the G1 phase of the cell cycle.
DOI of Published Version
Philos Trans R Soc Lond B Biol Sci. 2009 Mar 12;364(1517):645-52. Link to article on publisher's site
Philosophical transactions of the Royal Society of London. Series B, Biological sciences
Schrader, Carol E.; Guikema, Jeroen E. J.; Wu, Xiaoming; and Stavnezer, Janet, "The roles of APE1, APE2, DNA polymerase beta and mismatch repair in creating S region DNA breaks during antibody class switch" (2008). Open Access Articles. 2193.