Mechanism of error-free DNA synthesis across N1-methyl-deoxyadenosine by human DNA polymerase-?.

ABSTRACT: N1-methyl-deoxyadenosine (1-MeA) is formed by methylation of deoxyadenosine at the N1 atom. 1-MeA presents a block to replicative DNA polymerases due to its inability to participate in Watson-Crick (W-C) base pairing. Here we determine how human DNA polymerase-? (Pol?) promotes error-free replication across 1-MeA. Steady state kinetic analyses indicate that Pol? is ~100 fold more efficient in incorporating the correct nucleotide T versus the incorrect nucleotide C opposite 1-MeA. To understand the basis of this selectivity, we determined ternary structures of Pol? bound to template 1-MeA and incoming dTTP or dCTP. In both structures, template 1-MeA rotates to the syn conformation but pairs differently with dTTP versus dCTP. Thus, whereas dTTP partakes in stable Hoogsteen base pairing with 1-MeA, dCTP fails to gain a "foothold" and is largely disordered. Together, our kinetic and structural studies show how Pol? maintains discrimination between correct and incorrect incoming nucleotide opposite 1-MeA in preserving genome integrity.

SUBMITTER: Jain R 

PROVIDER: S-EPMC5341039 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature