Disease relevance of xis

• The DNA sequence of the int and xis genes of lambda bacteriophage, as well as that of the PI promoter and a region of unknown function beyond this, was determined by the chain termination procedure [1].
• Excision of the lambda prophage from the chromosome of its Escherichia coli host requires the products of the two viral genes int and xis [2].
• The predicted øg1e xis protein (Xis) is small and very acidic (66 amino acids; pI 4.55), and shows a resemblance (32% overall identity) with a putative excisionase encoded by the Staphylococcus phage ø11 [3].

High impact information on xis

• We report here the nucleotide sequence surrounding one of these loci, chi B, located between the xis and reda genes [4].
• The end of the xis gene in its turn overlaps the start of the int gene by 23 base pairs, in a different reading frame [1].
• DNA sequencing analysis of a 5.2-kbp SacI fragment of the øg1e phage genome (42.5 kbp) revealed two possible open reading frames (ORF), xis and int, and the phage attachment (recombination) site (attP), whose 24-bp sequence is identical to the core sequence detected in attR and attL [3].

Biological context of xis

• After transduction of each copy, a helper plasmid bearing phage lambda xis and int genes is introduced into the cells to excise the drug resistance gene flanked with the lambda attL and lambda attR sites from the chromosome [5].

References