Use of a linear multicopy vector based on the mini-replicon of temperate coliphage N15 for cloning DNA with abnormal secondary structures.

A new cloning vector pN15L is described. It is a linear 13.8 kb plasmid based on the coliphage N15 mini-replicon. The vector capacity exceeds 50 kb and the copy number is 250 per Escherichia coli chromosome. We show that some artificial and natural palindromes and approximately 5% of human DNA Bgl II fragments can be cloned effectively in linear vector pN15L, whereas they either sharply reduce the copy number of circular vector pUC19 or cannot be cloned at all. We conclude that pN15L may be usefully employed to clone large imperfect palindromes and some abnormal sequences of human DNA.