Persistent Link:
http://hdl.handle.net/10150/186021
Title:
Characterization of the repressor from the lambdoid phage HK022.
Author:
Carlson, Noel Gene.
Issue Date:
1992
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The lambdoid coliphage HK022 can grow in either a lytic or lysogenic mode following infection. In λ phage the switch to either mode is controlled by the cI and Cro repressors which bind to operators in the λ chromosome and regulate gene expression of adjacent promoters. HK022 is organized similar to λ, but has its own unique repressors and operators which are different from λ. The major goal of this research was to characterize the properties of the CI repressor from HK022 to understand better how this protein regulates gene expression. Seven sites in HK022 with similar nucleotide sequences were identified by DNase I footprinting analyses as CI binding sites. Six were clustered in two groups of three, O(L)1-O(L)3 (operator left) and O(R)1-O(R)3 (operator right), while the remaining site O(FR) (operator far right), was alone. The positions of these sites on the HK022 chromosome from left to right was O(L)1-O(L)3, cI, O(R)3-O(R)1, cro, and O(FR). CI bound to adjacent operators, O(R)1 and O(R)2, with a high degree of cooperativity (cooperativity parameter, ω, of about 2000). When only a single site was present (as with O(FR)), the repressor also increased the affinity for adjacent non-specific DNA sites resulting in a "phased" pattern of binding. CI binding sites were defined as operators by analyses of virulent phage mutants, which were able to escape CI repression and grow on a lysogen. The vast majority of virulent mutants contained 2 mutations in O(R), with single mutations in O(R)1 and O(R)2, suggesting that mutations in both sites are required to overcome the high degree of cooperativity. However, one mutant contained only a single mutation in O(R) and a second mutation in the distant site, O(FR). When the single O(FR) mutation was recombined with a wild-type O(R), the resulting phage was not virulent, but virulent mutants arose from it at a high frequency by acquiring a single mutation in either O(R)1 or O(R)2. The mechanism of action by O(FR) is not understood.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dissertations, Academic.; Molecular biology.; Genetics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Biochemistry; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Little, John W.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleCharacterization of the repressor from the lambdoid phage HK022.en_US
dc.creatorCarlson, Noel Gene.en_US
dc.contributor.authorCarlson, Noel Gene.en_US
dc.date.issued1992en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe lambdoid coliphage HK022 can grow in either a lytic or lysogenic mode following infection. In λ phage the switch to either mode is controlled by the cI and Cro repressors which bind to operators in the λ chromosome and regulate gene expression of adjacent promoters. HK022 is organized similar to λ, but has its own unique repressors and operators which are different from λ. The major goal of this research was to characterize the properties of the CI repressor from HK022 to understand better how this protein regulates gene expression. Seven sites in HK022 with similar nucleotide sequences were identified by DNase I footprinting analyses as CI binding sites. Six were clustered in two groups of three, O(L)1-O(L)3 (operator left) and O(R)1-O(R)3 (operator right), while the remaining site O(FR) (operator far right), was alone. The positions of these sites on the HK022 chromosome from left to right was O(L)1-O(L)3, cI, O(R)3-O(R)1, cro, and O(FR). CI bound to adjacent operators, O(R)1 and O(R)2, with a high degree of cooperativity (cooperativity parameter, ω, of about 2000). When only a single site was present (as with O(FR)), the repressor also increased the affinity for adjacent non-specific DNA sites resulting in a "phased" pattern of binding. CI binding sites were defined as operators by analyses of virulent phage mutants, which were able to escape CI repression and grow on a lysogen. The vast majority of virulent mutants contained 2 mutations in O(R), with single mutations in O(R)1 and O(R)2, suggesting that mutations in both sites are required to overcome the high degree of cooperativity. However, one mutant contained only a single mutation in O(R) and a second mutation in the distant site, O(FR). When the single O(FR) mutation was recombined with a wild-type O(R), the resulting phage was not virulent, but virulent mutants arose from it at a high frequency by acquiring a single mutation in either O(R)1 or O(R)2. The mechanism of action by O(FR) is not understood.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academic.en_US
dc.subjectMolecular biology.en_US
dc.subjectGenetics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineBiochemistryen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairLittle, John W.en_US
dc.contributor.committeememberVierling, Elizabethen_US
dc.contributor.committeememberDieckmann, Carolen_US
dc.contributor.committeememberMount, David W.en_US
dc.contributor.committeememberMontfort, William R.en_US
dc.identifier.proquest9307681en_US
dc.identifier.oclc713922324en_US
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