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MUTATIONAL INTERACTIONS BETWEEN NEAR‐UV RADIATION AND DNA DAMAGING AGENTS IN Escherichia coli : THE ROLE OF NEAR‐UV‐INDUCED MODIFICATIONS IN GROWTH AND MACROMOLECULAR SYNTHESIS
Author(s) -
Moraes E. C. De,
Tyrrell R. M.
Publication year - 1983
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1983.tb08366.x
Subject(s) - escherichia coli , reversion , mutant , dna , macromolecule , mutation , chemistry , ultraviolet , biology , biophysics , genetics , gene , phenotype , physics , quantum mechanics
— The mutational interactions between near‐ultraviolet (near‐UV, 334 nm, 365 nm) radiation and DNA damaging agents (far‐UV (254 nm) and ethyl‐methanesulphonate (EMS)) were studied in strains of Escherichia coli B/r trp thy with different susceptibilities to near‐UV‐induced growth delay (wild‐type, rel and srd ). Far‐UV induced reversion to tryptophan independence is reduced while forward mutation to streptomycin is enhanced by prior exposure of the rel+ srd+ strains to near‐UV radiation. The observed interactions are reduced ( rel ) or absent ( srd ) in the two mutant strains as are the corresponding growth and macromolecular synthesis delays normally observed after near‐UV treatment. Quantitatively, the degree of interaction induced by near‐UV pre‐treatment correlates closely with the degree of protein synthesis inhibition. We propose a mechanism for the contrasting interactions at the two genetic loci based on the different pathways by which pre‐mutagenic lesions may be processed. The primary chromophore for the mutational interactions would appear to be 4‐thiouracil‐containing transfer RNA.