FX cloning: a simple and robust high-throughput cloning method for protein expression.

The immense amount of gene sequences available nowadays allows scientist to screen broadly for extraordinary proteins. Reliable cloning tools that allow the parallel processing of many targets are vital for the success of this strategy. The FX cloning procedure detailed here is such a straightforward and efficient tool. It is dedicated to the cloning of open reading frames (ORFs) with the final aim of expressing the corresponding proteins. FX cloning combines attractive features of established high-throughput cloning methods that were thus far not unified in one single method. It facilitates the subcloning of a sequence-verified ORF to a variety of expression vectors, but is sufficiently versatile to accept PCR products as well. Moreover, the common, but undesirable feature of extending target ORFs with long cloning-related sequences is avoided. It leads to the addition of only one amino acid to each side of the protein. As a consequence, only one primer pair or PCR product suffices to generate expression vectors for both N- and C-terminal translational fusions. FX cloning is highly efficient and economical in its use. The method is suited for high-throughput cloning projects and also for everyday cloning of single targets. FX cloning is based on the use of type IIS restriction enzymes and negative selection markers. The full procedure takes place in one pot in less than 3 h and does not require intermediate purification steps nor extensive handling. The method has proven to be very robust and suitable for all common expression systems.