title: Lambda integrase cleaves DNA in cis.
abstract: In the Int family of site-specific recombinases, DNA cleavage is accomplished by nucleophilic attack on the activated scissile phosphodiester bond by a specific tyrosine residue. It has been proposed that this tyrosine is contributed by a protomer bound to a site other than the one being cleaved ('trans' cleavage). To test this hypothesis, the difference in DNA binding specificity between closely related integrases (Ints) from phages lambda and HK022 was exploited to direct wild type Ints and cleavage- or activation-defective mutants to particular sites on bispecific substrates. Analysis of Int cleavage at individual sites strongly indicates that DNA cleavage is catalyzed by the Int bound to the cleaved site ('cis' cleavage). This conclusion contrasts with those from previous experiments with two members of the Int family, FLP and lambda Int, that supported the hypothesis of trans cleavage. We suggest explanations for this difference and discuss the implications of the surprising finding that Int-family recombinases appear capable of both cis and trans mechanisms of DNA cleavage.
authors.affiliation: Division of Biology and Medicine, Brown University, Providence, RI 02912.
authors.forename: S E
authors.initials: SE
authors.lastname: Nunes-Düby
authors.forename: R S
authors.initials: RS
authors.lastname: Tirumalai
authors.forename: L
authors.initials: L
authors.lastname: Dorgai
authors.forename: E
authors.initials: E
authors.lastname: Yagil
authors.forename: R A
authors.initials: RA
authors.lastname: Weisberg
authors.forename: A
authors.initials: A
authors.lastname: Landy
mesh_terms: D010582:Bacteriophage lambda / Q000201:enzymology*; D004247:DNA / Q000378:metabolism*; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D004261:DNA Replication; D019426:Integrases; D008957:Models, Genetic; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D011995:Recombination, Genetic; D013379:Substrate Specificity; D016662:Virus Integration
chemical_list: D004247:DNA; D004254:DNA Nucleotidyltransferases; D019426:Integrases