RETROFITTING HIGH-MOLECULAR-WEIGHT DNA CLONED IN P1 - INTRODUCTION OFREPORTER GENES, MARKERS SELECTABLE IN MAMMALIAN-CELLS AND GENERATION OF NESTED DELETIONS

The bacteriophage P1 cloning system is proving to be quite useful for the cloning and analysis of genomic DNA inserts of up to 95 kb in size . In an effort to use that DNA directly in biological experiments we h ave embarked on a scheme to retrofit the P1 DNA using a mini-Tn10 tran sposon system. This transposon system is used in two ways: (i) to intr oduce a variety of sequence signals that are recognizable in mammalian cells, such as mammalian cell-responsive resistance markers and repor ter genes, and (ii) to generate a nested set of deletions in a P1 clon e by using a loxP site located within the transposon. In this report w e show that such transpositions into P1 DNA are efficient, distributed throughout the entire length of the genomic fragment and do not disru pt the DNA in any location other than the site of insertion of the tra nsposon. The TnlO-based P1 transduction system described here provides a general scheme for retrofitting any large genomic DNA cloned in a P 1 vector, thus facilitating the use of clones from the current P1 reco mbinant libraries in cellular transformation studies.