Journal
SCIENCE ADVANCES
Volume 7, Issue 29, Pages -Publisher
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/sciadv.abg0076
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Funding
- GIST Research Institute (GRI)
- National Research Foundation of Korea (NRF) - Korean government [NRF-2020R1A2C2006712, NRF-2019R1A4A1028802]
- Korean Health Technology R&D Project, Ministry of Health and Welfare, Republic of Korea [HA17C0031, 1720050]
- Korea Health Promotion Institute [1720050] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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The study reveals that during base excision repair, Exonuclease III creates a gap and transient ssDNA loop through an AP site anchor-based mechanism. The size of the gap is determined by the rigidity of the ssDNA loop and the duplex stability of the DNA.
During base excision repair, a transient single-stranded DNA (ssDNA) gap is produced at the apurinic/apyrimidinic (AP) site. Exonuclease III, capable of performing both AP endonuclease and exonuclease activity, are responsible for gap creation in bacteria. We used single-molecule fluorescence resonance energy transfer to examine the mechanism of gap creation. We found an AP site anchor-based mechanism by which the intrinsically distributive enzyme binds strongly to the AP site and becomes a processive enzyme, rapidly creating a gap and an associated transient ssDNA loop. The gap size is determined by the rigidity of the ssDNA loop and the duplex stability of the DNA and is limited to a few nucleotides to maintain genomic stability. When the 3' end is released from the AP endonuclease, polymerase I quickly initiates DNA synthesis and fills the gap. Our work provides previously unidentified insights into how a signal of DNA damage changes the enzymatic functions.
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