Deoxyribonucleic Acid Sequence Homologies Among Bacterial Insertion Sequence Elements and Genomes of Various Organisms

Abstract

Plasmid and phage deoxyribonucleic acid (DNA) harboring bacterial insertion sequence (IS) elements IS 1 , IS 2 , and IS 5 were characterized and used as probes to detect homologous sequences in various procaryotic and eucaryotic genomes. The hybridization method used permits the detection of sequences partially homologous to the elements. Hybridization of the IS-containing probes to each other revealed a region of limited homology between IS 1 and IS 2 . Homologous sequences were then detected by computer analysis of the published IS 1 and IS 2 nucleotide sequences. The homologous sequence contains a tandemly repeated tetranucleotide sequence which resembles the repeated sequence at the hot spot for spontaneous mutations in the lacI gene (P. J. Farabaugh, U. Schmeissner, M. Hofer, and J. Miller, J. Mol. Biol. 126: 847–863, 1978). Homology between the IS elements and various genomes was determined by hybridizing labeled DNA containing IS 1 , IS 2 , and IS 5 sequences to Southern blots of chromosomal DNA cleaved with restriction endonucleases. IS 1 and IS 5 appear limited to the enteric bacteria, whereas IS 2 sequences can also be detected in Pseudomonas putida, Pseudomonas aeruginosa , and Serratia marcescens . Bacteria which appear not to possess extrachromosomal elements, e.g., Caulobacter crescentus , did not show homology with any insertion sequences tested. In addition, sequences homologous to IS 1 , IS 2 , or IS 5 were not detected in Saccharomyces cerevisiae, Dictyostelium discoideum , or calf thymus DNA.