Nucleotide Excision Repair in Oocyte Nuclear Extracts from Xenopus laevis

We have developed efficient DNA repair extracts derived from the unusually large nuclei of Xenopus oocytes. These extracts use nucleotide excision repair (NER) to completely remove bulky adducts from DNA. There is very little or no synthesis on control, undamaged DNA, indicating the extracts do not have significant nonspecific nuclease activity, and repair of cyclobutane pyrimidine dimers (CPDs) occurs in the dark, indicating that NER, and not photolyase, is responsible for CPD repair. The extracts can be inactivated with antibodies specific to repair proteins and then repair activity can be restored by adding purified recombinant protein. Here we describe detailed protocols for preparing Xenopus nuclear repair extracts.