Influence of AlkB on 1,N2-ethenoguanine genotoxicity and mutagenicity in E. coli

TOXI 17

James C. Delaney, delaney@mit.edu1, Ivan D. Kozekov, ivan.kozekov@vanderbilt.edu2, Albena Kozekova2, Cintyu Wong, cywong@mit.edu3, Catherine L Drennan, cdrennan@mit.edu3, Lawrence J. Marnett, larry.marnett@vanderbilt.edu2, Carmelo J. Rizzo, c.j.rizzo@vanderbilt.edu2, and John M. Essigmann, jessig@mit.edu1. (1) Departments of Chemistry and Biological Engineering, Massachusetts Institute of Technology, Room 56-669, 77 Massachusetts Avenue, Cambridge, MA 02139, (2) Department of Chemistry, Center in Molecular Toxicology and the Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, TN 37235, (3) Department of Chemistry, Massachusetts Institute of Technology, 77 Mass Ave, Cambridge, MA 02139
A multitude of pathways exist for the formation of DNA damage from exogenous and endogenous reactive agents. One class of damage creates etheno-DNA lesions, whereby an unsaturated two-carbon unit bridges the exocyclic amino group and a ring nitrogen of either the adenine, cytosine, or guanine base. We have previously discovered that etheno-A and etheno-C are substrates for AlkB, which can directly reverse the etheno damage by epoxidation of the double bond, followed by hydrolysis of the epoxide to the diol, and jettisoning of the two carbon bridge as glyoxal. In the present work, we constructed a single-stranded viral genome containing 1,N2-ethenoguanine, which was passaged through AlkB(+) and AlkB(-) E. coli. Assays previously developed in our lab were used to assess the genotoxicity and mutagenicity of the lesion. We find that 1,N2-ethenoguanine gives predominantly -1 deletions, regardless of cell strain; however, G to A and G to T point mutations predominate when SOS-bypass polymerases are induced. While AlkB does diminish the amount of -1 deletions (and the amount of point mutations), the enzyme does not appear to act with vigor on 1,N2-ethenoguanine, as it weakly repaired an oligonucleotide containing the lesion (with respect to etheno-A), as analyzed by ESI-TOF mass spectrometry.
 

Young Investigator Session
8:15 AM-12:00 PM, Monday, August 20, 2007 BCEC -- 258C, Oral

Division of Chemical Toxicology

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007