Disease relevance of HK022p28

• Site-specific recombination in human cells catalyzed by the wild-type integrase protein of coliphage HK022 [1].
• Formation of such complexes, known as intasomes, is required for site-specific recombination catalysed by bacteriophage Lambda Integrase protein (Int) [2].
• These reactions occurred without the need to supply integration host factor and excisionase, the accessory proteins that are required for integrase-promoted site-specific recombination in vitro as well as in the natural host Escherichia coli [3].
• lambda integrase (Int) mediates recombination between attachment sites on lambda phage and E. coli DNAs [4].
• Tethering human immunodeficiency virus 1 integrase to a DNA site directs integration to nearby sequences [5].

High impact information on HK022p28

• The early events in site-specific excisive recombination were studied with phage lambda half-att sites that have no DNA to one side of the strand exchange region; they carry a single core-type integrase binding site and either P or P' arm flanking DNA [6].
• In addition, the data suggest that the two domains can bind DNA simultaneously, consistent with a model in which Integrase would link two disparate DNA sequences [7].
• A TYB-encoded protein, p90-TYB, contains amino acid sequences that are similar to those of retroviral integrase proteins [8].
• Flexibility in DNA recombination: structure of the lambda integrase catalytic core [9].
• Lambda integrase is archetypic of site-specific recombinases that catalyze intermolecular DNA rearrangements without energetic input [9].

Chemical compound and disease context of HK022p28

• Holliday junctions (HJ) are the central intermediates in both homologous recombination and site-specific recombination performed by tyrosine recombinases such as the bacteriophage lambda Integrase (Int) protein [10].
• In addition, we show that the lack of DDE-type integrase genes from elements of the DIRS1 group is explained by the finding that the previously uncharacterized ORFs of these elements encode proteins related to the site-specific recombinase of bacteriophage lambda [11].

Biological context of HK022p28

• Cells cotransfected with the substrate plasmid(s) and with a plasmid that expresses the wild-type Int show efficient integration as well as excision in both configurations [1].
• A critical regulator of this process is the phage-encoded excisionase (Xis) protein, which functions both as a DNA architectural factor and by cooperatively recruiting integrase to an adjacent binding site specifically required for excision [12].
• The excisionase (Xis) protein from bacteriophage lambda is the best characterized member of a large family of recombination directionality factors that control integrase-mediated DNA rearrangements [13].
• Tn916 and related conjugative transposons are clinically significant vectors for the transfer of antibiotic resistance among human pathogens, and they excise from their donor organisms using the transposon-encoded integrase ((Tn916)Int) and excisionase ((Tn916)Xis) proteins [14].
• These structures accommodate simultaneous binding of Int to direct-repeat arm sites and indirect-repeat core sites and afford a new view of the higher-order recombinogenic complexes [4].

Anatomical context of HK022p28

• Green monkey kidney cells (COS-1) and mouse embryo fibroblast cells (NIH3T3) transiently transfected with the recombinant plasmid express the integrase protein [3].
• Genetic manipulation of mouse embryonic stem cells by mutant lambda integrase [15].
• We also demonstrate that scIHF2 is stably expressed in HeLa cells, that it is localized primarily in the cell nucleus and that it triggers integrative recombination in mammalian cells by wild-type integrase [16].

Associations of HK022p28 with chemical compounds

• From this we have cloned and characterized a 188-amino acid, protease-resistant, carboxy-terminal fragment (C170) that we believe is the minimal catalytically competent domain of Int. C170 has topoisomerase activity and converts att suicide substrates to the covalent phosphotyrosine complexes characteristic of recombination intermediates [17].
• Int is a tyrosine recombinase that binds to DNA core sites via a C-terminal catalytic domain and to a collection of arm DNA sites, distant from the site of recombination, via its N-terminal domain [18].
• The mutant E47A, which was identified by alanine-scanning mutagenesis, abolishes interactions between Int and Xis bound at adjacent binding sites and reduces interactions between Int protomers bound at adjacent arm-type sites [19].
• Identification and characterization of the N-ethylmaleimide-sensitive site in lambda-integrase [20].
• Modulation of lambda integrase synthesis by rare arginine tRNA [21].

Other interactions of HK022p28

• The wild-type Int was active in the human cells without the need to supply the accessory proteins integration host factor (IHF) and excisionase (Xis) that are indispensable for the reaction in the bacterial host [1].

Analytical, diagnostic and therapeutic context of HK022p28

• The activity of the Integrase (Int) protein encoded by coliphage HK022 was tested in a human cell culture [1].
• Co-transfection of this plasmid with reporter plasmids for site-specific recombination and PCR analyses show that the integrase promotes site-specific integration as well as excision [3].
• A gel mobility shift assay has been used to show that, in the absence of accessory proteins, Int can align and hold together two DNA molecules, each with an attachment site, to form stable non-covalent 'bimolecular complexes'. Each attachment site must have both core and arm binding sites for Int to participate in a bimolecular complex [22].
• It is proposed that C170 is likely to represent a generic Int family domain that thus affords a specific route to studying the chemistry of DNA cleavage and ligation in these recombinases [17].
• NMR titration data with a peptide corresponding to Xis residues 57-69 strongly suggest that the carboxyl-terminal tail of Xis and the alpha-helix of the aminoterminal domain of Int comprise the primary interaction surface for these two proteins [19].

References