Translesion replication by DNA polymerase beta is modulated by sequence context and stimulated by fork-like flap structures in DNA

Mutations in the human genome are clustered in hot-spot regions, suggesting that some sequences are more prone to accumulate mutations than others. Th ese regions are therefore more likely to lead to the development of cancer. Several pathways leading to the creation of mutations may be influenced by the DNA sequence, including sensitivity to DNA damaging agents, and repair mechanisms. We have analyzed sequence context effects on translesion repli cation, the error-prone repair of single stranded DNA regions carrying lesi ons. By using synthetic oligonucleotides containing systematic variations o f sequences flanking a synthetic abasic site, we show that translesion repl ication by the repair polymerase DNA polymerase beta is stimulated to a mod erate extent by low stacking levels of the template nucleotides downstream of the lesion, combined with homopolymeric runs flanking the lesion both up stream and downstream. A strong stimulation of translesion replication by D NA polymerase beta was seen when fork-like flap structures were introduced into the DNA substrate downstream of the lesion. Unlike for gapped substrat es, this stimulation was independent of the presence of a phosphate group a t the 5' terminus of the flap. These results suggest that DNA polymerase be ta may participate in cellular DNA transactions involving higher order stru ctures. The significance of these results for in vivo translesion replicati on is discussed.