tailieunhanh - Báo cáo khoa học: The stereochemistry of benzo[a]pyrene-2¢-deoxyguanosine adducts affects DNA methylation by SssI and HhaI DNA methyltransferases

The biologically most significant genotoxic metabolite of the environmental pollutant benzo[a]pyrene (B[a]P), (+)-7R,8S-diol 9S,10R-epoxide, reacts chemically with guanine in DNA, resulting in the predominant formation of (+)-trans-B[a]P-N 2 -dG and, to a lesser extent, (+)-cis-B[a]P-N 2 -dG adducts. | ỊFEBS Journal The stereochemistry of benzo a pyrene-2z-deoxyguanosine adducts affects DNA methylation by SssI and HhaI DNA methyltransferases Oksana M. Subach1 Diana V. Maltseva1 Anant Shastry2 Alexander Kolbanovskiy2 Saulius Klimasauskas3 Nicholas E. Geacintov2 and Elizaveta S. Gromova1 1 Chemistry Department Moscow State University Russia 2 Department of Chemistry New York University NY USA 3 Laboratory of BiologicalDNA Modification Institute of Biotechnology Vilnius Lithuania Keywords benzo a pyrene-2 -deoxyguanosine adducts DNA methyltansferases environmental pollutants stereochemistry Correspondence E. S. Gromova Chemistry Department Moscow State University Moscow 119992 Russia Fax 7495 939 31 81 Tel 7495 939 31 44 E-mail gromova@ Received 19 July 2006 revised 19 January 2007 accepted 21 February 2007 doi The biologically most significant genotoxic metabolite of the environmental pollutant benzo a pyrene B a P -7R 8S-diol 9S 10R-epoxide reacts chemically with guanine in DNA resulting in the predominant formation of -trans-B a P-N2-dG and to a lesser extent -cis-B a P-N2-dG adducts. Here we compare the effects of the adduct stereochemistry and conformation on the methylation of cytosine catalyzed by two purified prokaryotic DNA methyltransferases MTases SssI and HhaI with the lesions positioned within or adjacent to their CG and GCGC recognition sites respectively. The fluorescence properties of the pyrenyl residues of the -cis-B a P-N2-dG and -trans-B a P-N2-dG adducts in complexes with MTases are enhanced but to different extents indicating that aromatic B a P residues are positioned in different microenvironments in the DNA-protein complexes. We have previously shown that the -trans-isomeric adduct inhibits both the binding and methylating efficiencies kcat of both MTases Subach OM Baskunov VB Darii MV Maltseva DV Alexandrov DA Kirsanova OV Kolbanovskiy A Kolbanovskiy M Johnson F Bonala R et al. 2006 .