Modulation of the 5â²-Deoxyribose-5-phosphate Lyase and DNA Synthesis Activities of Mammalian DNA Polymerase β by Apurinic/Apyrimidinic Endonuclease 1
The Ape1 protein initiates the repair of apurinic/apyrimidinic sites during mammalian base excision repair (BER) of DNA. Ape1 catalyzes hydrolysis of the 5â²-phosphodiester bond of abasic DNA to create nicks flanked by 3â²-hydroxyl and 5â²-deoxyribose 5-phosphate (dRP) termini. DNA polymerase (po...
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Published in | The Journal of biological chemistry Vol. 279; no. 24; p. 25268 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
American Society for Biochemistry and Molecular Biology
11.06.2004
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Online Access | Get full text |
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Summary: | The Ape1 protein initiates the repair of apurinic/apyrimidinic sites during mammalian base excision repair (BER) of DNA. Ape1
catalyzes hydrolysis of the 5â²-phosphodiester bond of abasic DNA to create nicks flanked by 3â²-hydroxyl and 5â²-deoxyribose
5-phosphate (dRP) termini. DNA polymerase (pol) β catalyzes both DNA synthesis at the 3â²-hydroxyl terminus and excision of
the 5â²-dRP moiety prior to completion of BER by DNA ligase. During BER, Ape1 recruits pol β to the incised apurinic/apyrimidinic
site and stimulates 5â²-dRP excision by pol β. The activities of these two enzymes are thus coordinated during BER. To examine
further the coordination of BER, we investigated the ability of Ape1 to modulate the deoxynucleotidyltransferase and 5â²-dRP
lyase activities of pol β. We report here that Ape1 stimulates 5â²-dRP excision by a mechanism independent of its apurinic/apyrimidinic
endonuclease activity. We also demonstrate a second mechanism, independent of Ape1, in which conditions that support DNA synthesis
by pol β also enhance 5â²-dRP excision. Ape1 modulates the gap-filling activity of pol β by specifically inhibiting synthesis
on an incised abasic substrate but not on single-nucleotide gapped DNA. In contrast to the wild-type Ape1 protein, a catalytically
impaired mutant form of Ape1 did not affect DNA synthesis by pol β. However, this mutant protein retained the ability to stimulate
5â²-dRP excision by pol β. Simultaneous monitoring of 5â²-dRP excision and DNA synthesis by pol β demonstrated that the 5â²-dRP
lyase activity lags behind the polymerase activity despite the coordination of these two steps by Ape1 during BER. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M400804200 |