3gv8

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.

Structural basis of error-prone replication and stalling at a thymine base by human DNA polymerase iota., Kirouac KN, Ling H, EMBO J. 2009 Jun 3;28(11):1644-54. PMID:19440206

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

Categories: DNA-directed DNA polymerase | Homo sapiens | Kirouac, K N. | Ling, H. | Dna damage | Dna repair | Dna replication | Dna synthesis | Dna-binding | Dna-directed dna polymerase | Error prone replication | Magnesium | Metal-binding | Mutator protein | Nucleotidyltransferase | Nucleus | Polymerase iota | Schiff base | Transferase | Transferase-dna complex | Y-family polymerase