A Switch in the Formation of Alternative DNA Loops Modulates λ Site-Specific Recombination

The virally encoded Xis protein is one of the components in the site-specific recombination reactions of bacteriophage λ. It is required for excisive recombination and inhibits integrative recombination. The mechanism of Xis inhibition of the integration reaction was investigated by methylation prot...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1991-01, Vol.88 (2), p.588-592
Main Authors: De Vargas, Lina Moitoso, Landy, Arthur
Format: Article
Language:English
Subjects:
Bacterial Proteins - metabolism
Bacteriophage lambda - genetics
Bacteriophages
Base Sequence
Bending
Binding sites
Biochemistry
Biological and medical sciences
Carrier Proteins - metabolism
DNA
DNA Nucleotidyltransferases - metabolism
DNA, Viral - genetics
DNA-Binding Proteins - metabolism
Escherichia coli - genetics
Escherichia coli Proteins
Fundamental and applied biological sciences. Psychology
Genetic mutation
Integration Host Factors
Kinetics
Methylation
Microbiology
Models, Genetic
Molecular Sequence Data
Nucleic Acid Conformation
Plasmids
Recombination, Genetic
Replicative cycle, interference, host-virus relations, pathogenicity, miscellaneous strains
Suicide
Viral Proteins
Virology
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Summary:The virally encoded Xis protein is one of the components in the site-specific recombination reactions of bacteriophage λ. It is required for excisive recombination and inhibits integrative recombination. The mechanism of Xis inhibition of the integration reaction was investigated by methylation protection assays (footprinting analyses) in conjunction with recombination assays. Xis is shown to mediate the formation of a specific attP looped structure involving cooperative and competitive long-range interactions among integrase, integration host factor, and Xis proteins. This higher-order structure precludes supercoiled attP from engaging in the productive partner interactions that lead to execution of the first strand exchange in integrative recombination. In addition to its previously characterized role in excision, Xis-induced DNA bending is postulated to act as a regulatory switch (in an alternative loop mechanism) that converts the attP intasome from an integrative-competent complex to a nonreactive one.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.88.2.588