Recombinant circle PCR and recombination PCR for site-specific mutagenesis without PCR product purification.

Two simple methods for site-specific mutagenesis are described and compared. In each method, the PCR is used in two separate amplifications to mutate the site of interest and to add ends to one PCR product that are homologous to the ends of the other PCR product. In the first method, the two products are combined, denatured and reannealed prior to transformation of E. coli in order to form recombinant circles in vitro, while in the second method, the two linear products are co-transfected directly into E. coli without prior manipulation, resulting in transformation of E. coli with the recombinant of interest by recombination in vivo. Each PCR amplification uses a plasmid template that has been linearized by restriction enzyme digestion outside the region to be amplified. This permits use of unpurified PCR products in these two protocols and generation of the mutant of interest with no other enzymatic manipulation in vitro apart from PCR amplification. In each protocol greater than or equal to 50% of the resulting clones contained the mutation of interest without detected errors.