Abstract
Although XPC-HR23B protein complex specifically binds to UV-induced (6-4) photoproduct, it also binds to non-damaged DNA non-specifically. Therefore, presence of a large excess of non-damaged DNA competitively inhibited the specific binding of XPC-HR23B to (6-4) photoproduct, thereby inhibiting nucleotide excision repair in vitro. This moderate damage specificity seems to be insufficient for XPC-HR23B to recognize a small number of lesions generated within the huge genomic DNA in cells. Since eukaryotic DNA is folded into nucleosomes, we examined effect of the nucleosome structure on the specific binding of XPC-HR23B to DNA damage. When non-damaged nucleosomal DNA was used as a competitor, the inhibitory effects on both the specific binding of XPC-HR23B to (6-4) photoproduct and the in vitro-nucleotide excision repair were suppressed. These results suggest that the presence of the nucleosome structure in non-damaged DNA regions may help specific targeting of XPC-HR23B to damaged sites by suppressing the non-specific DNA binding. [J Radiat Res 44:405 (2003)]
