Abstract: Methods, compositions and kits are disclosed for obtaining directionally truncated polypeptides by inserting a transposon. Preferably the transposon comprises a selectable marker and an ori, and optionally a promoter, a ribosome binding site and a translation start codon, into a target sequence in vitro or in vivo. Amplification products, varying in length depending on the transposon insertion site, are obtained using one primer that anneals to the target sequence and a second primer that anneals to the transposon. Amplification products are ligated to circular dsDNA, transformed into host cells, and individual colonies, each containing a directionally truncated clone of the target sequence, are obtained by plating on medium for which the selectable marker encodes resistance. Directionally truncated polypeptides encoded by the target sequence are obtained in vivo by inducing an RNAP in the host cells that uses the promoter or, in vitro by cell-free transcription and translation.

Abstract: A method for retrofitting DNA in a single-copy or high-copy vector, such as a fosmid or BAC, whereby an artificial transposon is used to introduce a conditional multi-copy origin of replication (“ori”) into the DNA in said vector. Following random in vitro or in vivo transposition of the ori-containing transposon into DNA in the single-copy or low-copy vector, the resulting insertion clones are introduced into a special host strain that contains a gene which encodes a polypeptide required for replication from the multi-copy ori. However, since the gene for this polypeptide is expressed from a tightly-regulated inducible promoter, the polypeptide is not expressed in the absence of inducer. On addition of inducer to the culture medium, the host cell synthesizes the polypeptide, which in turn activates replication from the multi-copy ori, thereby increasing the amount of clone DNA synthesized by the cell.

Abstract: In vitro production of RNA copies of either strand of any cloned DNA sequence may be obtained utilizing a unique cloning vector having two different opposed promoter sequences which are separated by a multiple cloning site. RNA polymerases which recognize only one of the particular promoter sequences in the vector may be applied to obtain transcription which proceeds from the recognized promoter toward the other promoter. Transcription of a desired strand of any DNA sequence is obtained by cleaving a particular restriction site in the multiple cloning site between the two promoter sequences, cloning the desired DNA sequence into the cleaved site, then cleaving another site between the two promoters which is distal to the promoter from which transcription is desired. The RNA polymerase which recognizes the selected promoter may then be applied to the vector to obtain transcription of the selected DNA sequence in vitro.