In vitro complementation of xeroderma pigmentosum.

In vitro complementation is a powerful strategy for isolation and characterization of individual components of multienzyme biochemical pathways. Application of the method to elucidate DNA metabolic pathways in prokaryotes enabled the successful identification of pathways of DNA replication and repair. In practice the technique requires the availability of genetic mutants that display defective operation of a selected biochemical pathway, and an in vitro assay system that allows detection of effective operation of the pathway. Xeroderma pigmentosum is a human disease syndrome characterized by partial or severe deficit in the operations of the nucleotidyl DNA excision repair pathway. This pathway of DNA repair appears to respond to DNA lesions which produce substantial distortion of helical structure, the best characterized of which are the UV radiation-induced pyrimidine dimers. This review summarizes a variety of approaches to analysis of the reparative deficiencies in xeroderma pigmentosum by in vitro complementation.