STRUCTURE OF THE HYDROGEN-BONDING COMPLEX OF O-6-METHYLGUANINE WITH CYTOSINE AND THYMINE DURING DNA-REPLICATION

Authors
Citation
Te. Spratt et De. Levy, STRUCTURE OF THE HYDROGEN-BONDING COMPLEX OF O-6-METHYLGUANINE WITH CYTOSINE AND THYMINE DURING DNA-REPLICATION, Nucleic acids research, 25(16), 1997, pp. 3354-3361
Citations number
41
Categorie Soggetti
Biology
Journal title
ISSN journal
03051048
Volume
25
Issue
16
Year of publication
1997
Pages
3354 - 3361
Database
ISI
SICI code
0305-1048(1997)25:16<3354:SOTHCO>2.0.ZU;2-3
Abstract
During DNA replication, mutations occur when an incorrect dNTP is inco rporated opposite a carcinogen-modified nucleotide. We have probed the structures of the interaction between O-6-methylguanine (O(6)mG) and cytosine and thymine during replication by kinetic means in order to e xamine the structure during the rate determining step. The kinetics of incorporation of dCTP and dTTP opposite O(6)mG and three analogs, S-G -methyl-6-thioguanine, O-6-methyl-1-deazaguanine and O-6-methylhypoxan thine, have been measured with four polymerases, the Klenow fragment o f DNA polymerase I, the Klenow fragment with the proof-reading exonucl ease inactivated, Tag and Tth polymerases. In the insertion of dTTP op posite O(6)mG, a large decrease in V-max/K-m was observed only upon mo dification of the N1 position. This result is consistent with a Watson -Crick type configuration. For the incorporation of dCTP, the V-max/K- m was significantly decreased only with removal of the exocyclic amino group at the 2 position. The pH dependence of the ratio of incorporat ion of dCTP and dTTP was independent of pH at physiological pH. This r esult suggests that dCTP is incorporated via an uncharged complex such as the wobble configuration.