Spectrum of mutations produced by specific types of restriction enzyme-induced double-strand breaks.

Rejoining of DNA double-strand breaks (DSB) plays a central role in the various processes leading to DNA rearrangements. We have analyzed DNA alterations induced by restriction enzymes that produce DSB with specific types of ends. Restriction enzymes were electroporated into a human lymphoblastoid cell line that stably maintains pHAZE, an EBV-based vector containing the lacZ gene. After allowing time for DSB repair, pHAZE DNA was rescued and screened in Escherichia coli. Mapping and sequence analysis of mutant copies of pHAZE indicated that restriction enzymes induced all classes of alterations except base substitutions (base deletions and insertions, large-scale deletions, inversions, and insertions). The spectra of alterations were distinctive for each enzyme and appear to be the consequence of specific end-modification processes.