THE ISOLATION AND CHARACTERIZATION OF AN OPERATOR CONSTITUTIVE MUTATION IN THE RECA GENE OF ESCHERICHIA COLI K-12.

Persistent Link:
http://hdl.handle.net/10150/143032
Title:
THE ISOLATION AND CHARACTERIZATION OF AN OPERATOR CONSTITUTIVE MUTATION IN THE RECA GENE OF ESCHERICHIA COLI K-12.
Author:
GINSBURG, HERSHEL.
Issue Date:
1982
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 lexA protein in E. coli is a specific repressor of the recA gene. The lexA protein is cleaved by the recA protein in response to DNA damage. Cleavage derepresses the recA gene resulting in high level synthesis of recA protein and the expression of other DNA damage inducible functions (SOS functions). The lexA3 mutation makes the lexA protein resistant to cleavage and thus inhibits expression of DNA damage inducible functions. A mutant of E. coli has been isolated which exhibits many of the properties expected of a strain carrying an operator-constitutive mutation in the recA gene. The mutation partially suppresses the UV sensitivity of lexA3 strains, maps near the recA structural gene, allows constitutive synthesis of the recA protein and the recA message, and is cis-acting. Strains carrying the recAo('c) mutation were used to study the role of amplified levels of recA protein in the expression of certain SOS functions. The recAo('c) mutation did not suppress the UV inhibitory effect of the lexA3 mutation on the expression of UV induced cellular mutagenesis, and the reactivation and mutagenesis of UV irradiated phage (lamda). The expression of these functions in lexA('+) strains was not enhanced by the recAo('c) mutation. Constitutive recA synthesis did not result in lethal filamentous growth. These results are consistent with those reported elsewhere that the expression of SOS function is not dependent on high levels of recA protein and that the various "SOS genes" are repressed by the lexA protein as is the recA gene. Thus, recA protein is required in SOS expression for the inactivation of lexA protein and recA amplification is a consequence, not a cause of SOS expression. The DNA sequence of the recA operator region from a (lamda)precA transducing phage thought to carry the recAo('c) mutation isolated here, was determined. No difference was detected between the supposed mutant DNA and wild type controls. The significance of these results and the possibility that the recAo('c) mutation was not transferred to the phage are discussed.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
DNA repair; Escherichia coli -- Genetics
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Medical and Molecular Microbiology; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Mount, David

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleTHE ISOLATION AND CHARACTERIZATION OF AN OPERATOR CONSTITUTIVE MUTATION IN THE RECA GENE OF ESCHERICHIA COLI K-12.en_US
dc.creatorGINSBURG, HERSHEL.en_US
dc.contributor.authorGINSBURG, HERSHEL.en_US
dc.date.issued1982en_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 lexA protein in E. coli is a specific repressor of the recA gene. The lexA protein is cleaved by the recA protein in response to DNA damage. Cleavage derepresses the recA gene resulting in high level synthesis of recA protein and the expression of other DNA damage inducible functions (SOS functions). The lexA3 mutation makes the lexA protein resistant to cleavage and thus inhibits expression of DNA damage inducible functions. A mutant of E. coli has been isolated which exhibits many of the properties expected of a strain carrying an operator-constitutive mutation in the recA gene. The mutation partially suppresses the UV sensitivity of lexA3 strains, maps near the recA structural gene, allows constitutive synthesis of the recA protein and the recA message, and is cis-acting. Strains carrying the recAo('c) mutation were used to study the role of amplified levels of recA protein in the expression of certain SOS functions. The recAo('c) mutation did not suppress the UV inhibitory effect of the lexA3 mutation on the expression of UV induced cellular mutagenesis, and the reactivation and mutagenesis of UV irradiated phage (lamda). The expression of these functions in lexA('+) strains was not enhanced by the recAo('c) mutation. Constitutive recA synthesis did not result in lethal filamentous growth. These results are consistent with those reported elsewhere that the expression of SOS function is not dependent on high levels of recA protein and that the various "SOS genes" are repressed by the lexA protein as is the recA gene. Thus, recA protein is required in SOS expression for the inactivation of lexA protein and recA amplification is a consequence, not a cause of SOS expression. The DNA sequence of the recA operator region from a (lamda)precA transducing phage thought to carry the recAo('c) mutation isolated here, was determined. No difference was detected between the supposed mutant DNA and wild type controls. The significance of these results and the possibility that the recAo('c) mutation was not transferred to the phage are discussed.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDNA repairen_US
dc.subjectEscherichia coli -- Geneticsen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineMedical and Molecular Microbiologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMount, Daviden_US
dc.identifier.proquest8304718en_US
dc.identifier.oclc683261124en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.