Structural basis of error-prone replication and stalling at a thymine base by human DNA polymerase
Human DNA polymerase iota (pol iota) is a unique member of Y-family polymerases, which preferentially misincorporates nucleotides opposite thymines (T) and halts replication at T bases. The structural basis of the high error rates remains elusive. We present three crystal structures of pol complexed with DNA containing a thymine base, paired with correct or incorrect incoming nucleotides. A narrowed active site supports a pyrimidine to pyrimidine mismatch and excludes Watson-Crick base pairing by pol. The template thymine remains in an anti conformation irrespective of incoming nucleotides. Incoming ddATP adopts a syn conformation with reduced base stacking, whereas incorrect dGTP and dTTP maintain anti conformations with normal base stacking. Further stabilization of dGTP by H-bonding with Gln59 of the finger domain explains the preferential T to G mismatch. A template 'U-turn' is stabilized by pol and the methyl group of the thymine template, revealing the structural basis of T stalling. Our structural and domain-swapping experiments indicate that the finger domain is responsible for pol's high error rates on pyrimidines and determines the incorporation specificity.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1005667
- Journal Information:
- EMBO J., Journal Name: EMBO J. Journal Issue: (11) ; 06, 2009 Vol. 28; ISSN EMJODG; ISSN 0261-4189
- Country of Publication:
- United States
- Language:
- ENGLISH
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