Abstract: The present invention relates to methods of joining two or more double-stranded (ds) or single-stranded (ss) DNA molecules of interest in vitro, wherein the distal region of the first DNA molecule and the proximal region of the second DNA molecule of each pair share a region of sequence identity. The method allows the joining of a large number of DNA fragments, in a predetermined order and orientation, without the use of restriction enzymes. It can be used, e.g., to join synthetically produced sub-fragments of a gene or genome of interest. Kits for performing the method are also disclosed. The methods of joining DNA molecules may be used to generate combinatorial libraries useful to generate, for example, optimal protein expression through codon optimization, gene optimization, and pathway optimization.

Abstract: The present invention relates, e.g., to in vitro method, using isolated protein reagents, for joining two double stranded (ds) DNA molecules of interest, wherein the distal region of the first DNA molecule and the proximal region of the second DNA molecule share a region of sequence identity, comprising contacting the two DNA molecules in a reaction mixture with (a) a non-processive 5? exonuclease; (b) a single stranded DNA binding protein (SSB) which accelerates nucleic acid annealing; (c) a non strand-displacing DNA polymerase; and (d) a ligase, under conditions effective to join the two DNA molecules to form an intact double stranded DNA molecule, in which a single copy of the region of sequence identity is retained. The method allows the joining of a number of DNA fragments, in a predetermined order and orientation, without the use of restriction enzymes.