Error -prone translesion synthesis with human DNA polymerase eta on DNA containing 3,4-dihydroxy-1,2-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene dA adducts

Human DNA polymerase eta was used to copy four stereoisomeric trans and cis ring opened benzo[c]phenanthrene 1,2,3,4-tetrahydro-3,4-diol-1,2-epoxide adducts placed on the N6 position of dA residues. Utilizing sequence 3 ' CGTCGAGATTT*AGAC 5', incorporation of G, A, T, and C were observed using templates containing trans R, trans S, cis R, and cis S ring opened adducts. Incorporation of dNTPs across from the adducts occurred primarily at a similar or lower rate than undamaged DNA. Trans S and cis S adducts, however, had several dNTP incorporations that occurred at slightly higher rates. The same two isomers showed remarkable rates of extension of (mis)incorporation. The extension rate at trans S adducts showed an increase for G, A, T and C pairs with adducted A of 6.5x, 1.6x, 2.7x and 1.2x respectively over the rates for non-adducted (undamaged) DNA. Cis S extension of (mis)incorporation showed a dramatic increase over non-adducted DNA for all 4 bases, G. A, T, and C of 9.1x, 20x, 14x, and 3.1x respectively. Trans R and cis R adducts both inhibit DNA extension. The active site of pol eta seems to prefer adducts in the S position during extension but not during incorporation. The position of the adduct in the DNA may interfere with extension at R adducts but not at S adducts. It is suggested that the rate-limiting step of nucleotide incorporation by DNA polymerase eta during extension is eliminated by trans S and cis S isomers only.