Talk abstracts
Talk on Wednesday 03:15-03:30pm submitted by Andrew Reed
Viewing human DNA polymerase β faithfully and unfaithfully bypass an oxidative lesion by time-dependent crystallography
Andrew J. Reed (Department of Chemistry and Biochemistry, Ohio State Biochemistry Program), Rajan Vyas (Department of Chemistry and Biochemistry), E. John Tokarsky (Department of Chemistry and Biochemistry, Ohio State Biophysics Graduate Program), Zucai Suo (Department of Chemistry and Biochemistry, Ohio State Biochemistry Program, and Ohio State Biophysics Graduate Program)
Abstract:
One common oxidative DNA lesion, 8-oxo-7,8-dihydro-2′-deoxyguanine (8-oxoG), is highly mutagenic in vivo due to its anti-conformation forming a Watson-Crick base pair with correct deoxycytidine 5′-triphosphate (dCTP) and its syn-conformation forming a Hoogsteen base pair with incorrect deoxyadenosine 5′-triphosphate (dATP). Here, we utilized time-resolved X-ray crystallography to follow 8-oxoG bypass by human DNA polymerase β (hPolβ). In the 12 solved structures, both Watson-Crick (anti-8-oxoG:anti-dCTP) and Hoogsteen (syn-8-oxoG:anti-dATP) base pairing were clearly visible and were maintained throughout the chemical reaction. Additionally, a third Mg2+ appeared during the process of phosphodiester bond formation and was located between the reacting α- and β-phosphates of the dNTP, suggesting its role in stabilizing reaction intermediates. After phosphodiester bond formation, hPolβ reopened its conformation, pyrophosphate was released, and the newly incorporated primer 3′-terminal nucleotide stacked, rather than base paired, with 8-oxoG. These structures provide the first real-time pictures, to our knowledge, of how a polymerase correctly and incorrectly bypasses a DNA lesion.
Keywords: X-ray Crystallography, DNA polymerases, oxidative damage