Spontaneous and mutagen-induced deletions: mechanistic studies in Salmonella tester strain TA102

Journal Article · Sun Jul 01 04:00:00 EDT 1984 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.81.14.4457· OSTI ID:5997388

Levin, D E; Marnett, L J; Ames, B N

Salmonella tester strain TA102 carries the hisG428 ochre mutation on the multicopy plasmid pAQ1. DNA sequence analysis of 45 spontaneous revertants of hisG428 on the chromosome in the presence of pKM101 (strain TA103) indicates that hisG428 revertants fall into three major categories: (i) small, in-frame deletions (3 or 6 base pairs) that remove part or all of the ochre triplet; (ii) base substitution mutations at the ochre site; (iii) extragenic ochre suppressors. Deletion revertants are identified in a simple phenotypic screen by their resistance to the inhibitory histidine analog thiazolealanine, which feedback inhibits the wild-type hisG enzyme but not the enzyme resulting from the deletions. The effect of various genetic backgrounds on the generation of spontaneous deletion revertants was examined. The presence of a uvrB mutation or a recA mutation suppressed the generation of spontaneous deletion revertants to approximately 1/2.5. When hisG428 was in multiple copies on pAQ1, the frequency of spontaneous deletion revertants increased by 40-fold, which is the approximate copy number of pAQ1. Mutagenic agents that induce single-strand breaks in DNA (e.g., x-rays, bleomycin, and nalidixic acid) induced deletion revertants in TA102. These agents induced deletion revertants only in hisG428 on pAQ1 and only in the presence of pKM101. Deletion revertants were not induced by frameshift mutagens (i.e., ICR-191 and 9aminoacridine). These results indicate that different pathways exist for the generation of spontaneous and mutagen-induced deletion revertants of hisG428. 41 references, 2 figures, 3 tables.

• Research Organization: Univ. of California, Berkeley
• DOE Contract Number: AT03-76EV70156
• OSTI ID: 5997388
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 81:14; ISSN PNASA
• Country of Publication: United States
• Language: English

Related Subjects

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63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALANINES
AMINO ACIDS
ANTI-INFECTIVE AGENTS
ANTIBIOTICS
ANTIMITOTIC DRUGS
ANTINEOPLASTIC DRUGS
AZOLES
BACTERIA
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
BLEOMYCIN
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHROMOSOMES
DNA
DNA REPAIR
DNA SEQUENCING
DRUGS
ELECTROMAGNETIC RADIATION
ENZYME INHIBITORS
GENES
HETEROCYCLIC COMPOUNDS
IONIZING RADIATIONS
MICROORGANISMS
MUTAGEN SCREENING
MUTANTS
MUTATIONS
NUCLEIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PLASMIDS
RADIATIONS
RECOVERY
REPAIR
REVERTANTS
SALMONELLA
SCREENING
STRAND BREAKS
STRUCTURAL CHEMICAL ANALYSIS
THIAZOLES
X RADIATION