Repair of U/G and U/A in DNA by UNG2-associated repair complexes takes place predominantly by short-patch repair both in proliferating and growth-arrested cells.
Nuclear uracil-DNA glycosylase UNG2 has an established role in repair of U/A pairs resulting from misincorporation of dUMP during replication. In antigen-stimulated B-lymphocytes UNG2 removes uracil from U/G mispairs as part of somatic hypermutation and class switch recombination processes. Using antibodies specific for the N-terminal non-catalytic domain of UNG2, we isolated UNG2-associated repair complexes (UNG2-ARC) that carry out short-patch and long-patch base excision repair (BER). These complexes contain proteins required for both types of BER, including UNG2, APE1, POLbeta, POLdelta, XRCC1, PCNA and DNA ligase, the latter detected as activity. Short-patch repair was the predominant mechanism both in extracts and UNG2-ARC from proliferating and less BER-proficient growth-arrested cells. Repair of U/G mispairs and U/A pairs was completely inhibited by neutralizing UNG-antibodies, but whereas added recombinant SMUG1 could partially restore repair of U/G mispairs, it was unable to restore repair of U/A pairs in UNG2-ARC. Neutralizing antibodies to APE1 and POLbeta, and depletion of XRCC1 strongly reduced short-patch BER, and a fraction of long-patch repair was POLbeta dependent. In conclusion, UNG2 is present in preassembled complexes proficient in BER. Furthermore, UNG2 is the major enzyme initiating BER of deaminated cytosine (U/G), and possibly the sole enzyme initiating BER of misincorporated uracil (U/A).
Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, N-7489 Trondheim, Norway.
Mansour
M
Akbari
Marit
M
Otterlei
Javier
J
Peña-Diaz
Per Arne
PA
Aas
Bodil
B
Kavli
Nina B
NB
Liabakk
Lars
L
Hagen
Kohsuke
K
Imai
Anne
A
Durandy
Geir
G
Slupphaug
Hans E
HE
Krokan
D002455:Cell Division; D002460:Cell Line; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D045647:DNA Glycosylases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000502:physiology; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D011233:Precipitin Tests; D013379:Substrate Specificity; D014498:Uracil / Q000378:metabolism; D051981:Uracil-DNA Glycosidase; D000076105:X-ray Repair Cross Complementing Protein 1
D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human; D014498:Uracil; D004247:DNA; C492570:CCNO protein, human; D045647:DNA Glycosylases; C498095:SMUG1 protein, human; D051981:Uracil-DNA Glycosidase; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase