Indirect suppression of radiation sensitivity of a recA$sup -$ strain of Escherichia coli K12

Conference · Wed Jan 01 04:00:00 EST 1975

OSTI ID:4111216

Mount, D W; Walker, A C; Kosel, C; Hanawalt, P C ^[1]

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1. ed.

It has been shown previously that the radiation sensitivity of LexA$sup - $ strains of Escherichia coli K-12 can be suppressed by thermosensitive mutations (designated tsl) that are closely linked to the lexA locus. These are thought to be intragenic suppressors that reduce the activity of the diffusible product that gives rise to the lexA$sup -$ phenotype (Mount et al., 1973). When a recA mutation is crossed into a suppressed tsl$sup -$ strain, the extreme radiation sensitivity usually conferred by a recA mutation is considerably reduced without any detectable change in genetic recombination deficiency. Suppression of uv sensitivity depends upon the activity of the uvrA$sup +$ product. We propose that at least part of the radiation sensitivity of a recA$sup -$ strain is due to a DNA repair defect that is different from inability to perform genetic exchanges and depends upon the presence of the lexA$sup +$ product. We hypothesize that the lexA$sup +$ product is a repressor of the synthesis of repair enzymes. In recA$sup +$ cells with DNA lesions, repressor is inactivated leading to enzyme induction but this does not occur in recA$sup -$ cells. tsl mutations inactivate repressor leading to constitutive enzyme synthesis and bypassing the need for recA$sup +$ product to inactivate the lexA$sup +$ product. (auth)

• Research Organization: Univ. of Arizona, Tucson
• NSA Number: NSA-33-012284
• OSTI ID: 4111216
• Country of Publication: United States
• Language: English

Related Subjects

*DNA-- BIOLOGICAL REPAIR
*ESCHERICHIA COLI-- RADIOSENSITIVITY
*MUTATIONS-- RADIOINDUCTION
560131* --Biomedical Sciences
Applied Studies--Radiation Effects--Radiation Effects on Microorganisms--Basic Studies
BIOLOGICAL RADIATION EFFECTS
ENZYMES
GENE RECOMBINATION
N48310* --Life Sciences--Radiation Effects on Microorganisms- -Basic Studies
ULTRAVIOLET RADIATION