DNA repair in congenic mice: possible influence of a chromosome 4 genetic region on the rate of benzo[a]pyrene-induced DNA adduct removal

An attempt was made to assign mouse lifespan-associated interstrain differences in DNA repair to a specific chromosomal region using a set of congenic mice. The sensitive 32P-postlabeling assay was employed to measure the removal of benzo[a]pyrene-induced DNA adducts in liver DNA of three different chromosome 4 congenic mouse strains: B6.C-H-15c, B6.C-H-16c, and B6.C-H-26c and the two parental strains, C57B1/6 and BALB/c. The removal of the one main adduct detected, trans-(7R)-N2-[10-(7 beta,8 alpha,9 alpha-trihydroxy)-7,8,9,10- tetrahydrobenzo(a)-pyrene]-yl-deoxyguanosine (BPDE-N2-dG), in liver DNA of C57Bl/6 and BALB/c mice between one and three days after treatment, was approximately 86% and 57%, respectively. The percentage removal of BPDE-N2-dG in two of the three congenic mouse strains, B6.C-H-16c and B6.C-H-26c, resembled that found in BALB/c, whereas the third strain, B6.C-H-15c, removed about the same amount as C57B1/6, i.e., approximately 88% of BPDE-N2-dG between one and three days after treatment. The usefulness of congenic mouse strains for identifying genes putatively involved in aging and/or disease susceptibility is discussed.