A GENETIC ANALYSIS OF NEW ASPECTS OF DNA REPAIR IN ESCHERICHIA COLI K-12

Persistent Link:
http://hdl.handle.net/10150/282019
Title:
A GENETIC ANALYSIS OF NEW ASPECTS OF DNA REPAIR IN ESCHERICHIA COLI K-12
Author:
Pacelli Rassenti, Laura Zina
Issue Date:
1981
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:
When the DNA of Escherichia coli is damaged a set of events termed "SOS functions" occur to aid cellular survival. The recA and lexA proteins are involved in the regulation of these functions. To determine the role of the lexA protein, amber mutations, designated spr-55(amber), were isolated in the lexA-3 gene. The lack of the lexA-3 gene product abolished sensitivity to ultraviolet light and resulted in the constitutive synthesis of recA protein. Introduction of amber suppressor mutations restored the original lexA-3 phenotype. It was concluded that spr mutations inactivate lexA protein resulting in the constitutive expression of the SOS functions. These data provide evidence that the lexA protein is the repressor for the recA gene. The repair of phage lambda (λ⁺) by ultraviolet light was determined in the strains carrying alleles of the spr, uvrA, and recA genes. The survival of the phage was more in the spr-51 uvrA⁺ strain as compared to wild type. These results were not dependent on the recA genotype. Introduction of the uvrA-6 mutation into the spr-51 uvrA⁺ recA⁺ strains resulted in the same relative decrease of phage survival. These results suggest that lexA protein is involved in the regulation of uvrA-dependent excision repair and that inactivation of lexA leads to the constitutive expression of excision repair. New mutant forms of lexaA protein were isolated. The lexA⁺, lexA-3, lexA-10, and lexA-27 proteins displayed identical mobilities in the Weber and Osborn gel system. The lexA-10 and lexA-27 genes showed different phenotypes and encoded proteins of different mobilities in the Laemmli gel system. It was concluded that the differences in mobilities observed in the Laemmli gel system are due to alterations in charge or amino acid, not in size; furthermore; the molecular weight of lexA⁺ protein was determined to be 24 kilodaltons.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Escherichia coli.; DNA repair.; Bacterial genetics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Genetics
Degree Grantor:
University of Arizona
Advisor:
Mount, David

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleA GENETIC ANALYSIS OF NEW ASPECTS OF DNA REPAIR IN ESCHERICHIA COLI K-12en_US
dc.creatorPacelli Rassenti, Laura Zinaen_US
dc.contributor.authorPacelli Rassenti, Laura Zinaen_US
dc.date.issued1981en_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.abstractWhen the DNA of Escherichia coli is damaged a set of events termed "SOS functions" occur to aid cellular survival. The recA and lexA proteins are involved in the regulation of these functions. To determine the role of the lexA protein, amber mutations, designated spr-55(amber), were isolated in the lexA-3 gene. The lack of the lexA-3 gene product abolished sensitivity to ultraviolet light and resulted in the constitutive synthesis of recA protein. Introduction of amber suppressor mutations restored the original lexA-3 phenotype. It was concluded that spr mutations inactivate lexA protein resulting in the constitutive expression of the SOS functions. These data provide evidence that the lexA protein is the repressor for the recA gene. The repair of phage lambda (λ⁺) by ultraviolet light was determined in the strains carrying alleles of the spr, uvrA, and recA genes. The survival of the phage was more in the spr-51 uvrA⁺ strain as compared to wild type. These results were not dependent on the recA genotype. Introduction of the uvrA-6 mutation into the spr-51 uvrA⁺ recA⁺ strains resulted in the same relative decrease of phage survival. These results suggest that lexA protein is involved in the regulation of uvrA-dependent excision repair and that inactivation of lexA leads to the constitutive expression of excision repair. New mutant forms of lexaA protein were isolated. The lexA⁺, lexA-3, lexA-10, and lexA-27 proteins displayed identical mobilities in the Weber and Osborn gel system. The lexA-10 and lexA-27 genes showed different phenotypes and encoded proteins of different mobilities in the Laemmli gel system. It was concluded that the differences in mobilities observed in the Laemmli gel system are due to alterations in charge or amino acid, not in size; furthermore; the molecular weight of lexA⁺ protein was determined to be 24 kilodaltons.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectEscherichia coli.en_US
dc.subjectDNA repair.en_US
dc.subjectBacterial genetics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineGeneticsen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMount, Daviden_US
dc.identifier.proquest8128335en_US
dc.identifier.oclc8712786en_US
dc.identifier.bibrecord.b1391831xen_US
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