Balanced-size and long-size cloning of full-length, cap-trapped cDNAs intovectors of the novel lambda-FLC family allows enhanced gene discovery rateand functional analysis

We have developed a new class of cloning vectors: lambda -full-length cDNA (lambda -FLC) cloning vectors. These vectors can be bulk-excised for prepar ing full-length cDNA libraries in which a high proportion of the plasmids c arry large inserts that can be transferred into other (for example, functio nal) vectors. Unlike other cloning vectors, lambda -FLC vectors accommodate a broad range of sizes of eukaryotic cDNA inserts because they contain "si ze balancers." Further, the main protocol we use for direct bulk excision o f plasmids is mediated by a Cre-lox system and is apparently free of size b ias. The average size of the inserts from excised plasmid cDNA libraries wa s 2.9 kb for standard and 6.9 kb for size-selected cDNA. The average insert size of the full-length cDNA libraries was correlated to the rate of new g ene discovery, suggesting that effectively cloning rarely expressed mRNAs r equires vectors that can accommodate large inserts from a variety of source s. Part of the vectors are also suitable for bulk transfer of inserts into various functional vectors.