Competitive priming PCR: a versatile method to generate cohesive terminus.

In the post-genomic era, providing a detailed description of protein functions poses a formidable challenge. To gain functional insights, we have to construct many kinds of expression vectors. DNA recombination based on polymerase chain reaction (PCR) and digestion followed by ligation is the preferred method for vector construction. However, this existing pattern is intrinsically limited by the selection of restriction endonuclease, prompting researchers to use commercial suppliers rather than amplifying genes themselves. Moreover, this method would introduce additional bases into the PCR products, which may be undesired for the construction of epitope expressing plasmid. A PCR-based gene synthesis method, referred to as competitive priming PCR (CP-PCR), is described here to efficiently assemble the plasmid expressing fusion protein of fibrinogen alpha chain and binding domain of galactose transcription factor. A pair of competitive sense primers were designed for the same target sequence. With the presence of antisense primer, PCR amplification of target sequence was performed in the same one system. The PCR product was underwent single digestion by using PstI, followed by ligation with the vector pCMV-BD linearized with EcoRIand PstI. The reconstructed plasmid was validated by sequencing and the fusion protein was affirmed by western blot. CP-PCR combines the superior convenience and precision of PCR. Moreover, it is perfectly capable of generating nearly all kinds of cohesive terminuses, which are ready to recombination in the presence of single digestion or even in the absence of digestion. We demonstrate, by using CP-PCR, the feasibility of directed cloning interested sequence only in the requirement of single digestion or even in the absence of digestion. Competitive priming PCR is demonstrated with convenience and precision equivalent to the traditional method. More than that, "seamless" DNA recombination may be achieved by this novel strategy.