Provided are methods, compositions, and kits for molecular cloning of DNA using DNA topoisomerase. The methods comprise (I) combining into a mixture (A) a first polynucleotide, comprising an origin of replication, a selectable marker, two topoisomerase recognition sequences, and two nicking agent recognition sequences, each of the topoisomerase recognition sequences being within 50 nucleotides of at least one of the nicking agent recognition sequences and each of two nicking agent recognition sequences being nicked, with (B) a sequence-specific topoisomerase and (C) a second polynucleotide, having a 5′ hydroxyl on each end; and (II) transforming the mixture into a host organism, thereby cloning the second polynucleotide. Formation or purification of a DNA-protein adduct prior to the addition of the second polynucleotide is not required. Also provided are vector sequences to facilitate performance of the methods and methods for modifying a vector of interest to render it useful in the disclosed methods.