Figure 4.

Effect of the presence of various types of SSBs on the excision of 8-oxoG by yOGG1. The oligonucleotide containing an AP site at positions 5 bases 5′ (–5) to 5 bases 3′ (+5) opposite 8-oxoG or no damage opposite 8-oxoG were treated with either Nth (A) or HAP1 (B) as described in Materials and Methods to obtain either a β-SSB or a HAP1-SSB, respectively. The β–δ-SSB (C) was obtained by hybridisation of the radiolabelled 8-oxoG-containing oligonucleotide with two oligonucleotides corresponding to the strand 1 sequence but with a gap at the various positions Y and containing 3′P and 5′P termini around the gap. Oligonucleotides were then subjected to excision of 8-oxoG by yOGG1 and the efficiency of excision of 8-oxoG was measured after migration of the samples on a 12% denaturing polyacrylamide gel. The diagrams reflect the fold inhibition/activation by comparison to the control without damage on the non-labelled strand. The error bars represent the standard deviation from three to four different experiments. The structures of the SSB are shown schematically with an arbitrary choice of base pairs for illustrative purposes; a filled circle represents a phosphate group.