Radiation-Sensitive Mutants

Maezawa, H. Furusawa, Y. Kobayashi, K. Hieda, K. Suzuki, M. Usami, N. Yokoya, A. Mori, T. Lethal effect of K-shell absorption of intracellular phosphorus on wild- type and radiation sensitive mutants of Escherichia coli [published erratum appears in Acta Oncol. 1997 36(2) 238] Acta Oncol. 1996, 35 (7), 889-894. 

This example inspired searches for radiation sensitive mutants in yeast. The way was led by Nakai and Matsumoto (1967) who isolated one mutant, UV which was very sensitive to ultraviolet and a second, Xj sensitive to X-rays. They went one step further than isolation and survival curves by making the double-mutant and showing that like double mutants of recA and uvr A in E. coli it was much more sensitive to UV than either single mutant alone. This was the first demonstration of the existence of more than one type or pathway of DNA repair of UV damage in yeast, and inspired the later work of Game and Cox (1972 1973 1974), Brendel and Haynes (1973) and Louise Prakash (1993) in the genetic analysis of pathways of repair in yeast. This led to the classification of the many mutant loci into epistasis groups, which are defined as those mutants which, when combined in the same strain, are no more UV-sensitive than the most sensitive of the two when alone. 

Hill, R.F. (1958). A radiation-sensitive mutant of Escherichia coli. Biochem. Biophys. Acta 30,636-637. 

Holliday, R. (1965b). Radiation sensitive mutants of Ustilago maydis. Mutation Res. 2, 557-559. 

Nakai, S. Matsumoto, K. (1967). T vo types of radiation-sensitive mutants in yeast. Mutation Res. 4, 129-136. 

Mori, T. and Dizdaroglu, M. (1994) Ionizing radiation causes greater DNA base damage in radiation-sensitive mutant M10 cells than in parent mouse lymphoma L5178Y cells. Radiat. Res., 140, 65-90. 

T. Kada, Y. Sadaie, and K. Tutikawa, Microbial screening of mutagens and carcinogens, II. Utilization of radiation-sensitive mutant strains, Proc. Annu. Meet. Jpn. Assoc. Agric. Chem. 46, 4C-18 (1971) (in Japanese). 

Rutberg, L., Rutberg, B. Growth of bacteriophage 0105 and its deoxyribonucleic acid in radiation-sensitive mutants of Bacillus suhtilis. J. Virol. 8, 919-921 (1971). 

Boubnov NV, Hall KT, Wills Z, et al. Complementation of the ionizing radiation sensitivity, DNA end binding, and V(D)J recombination defects of double-strand break repair mutants by the p86 Ku autoantigen. Proc Natl Acad Sci USA 1995 92(3) 890-894. 

Error-Free Repair by Homologous Recombination Yeasts can repair double-strand breaks Induced by y-lrradlatlon. Isolation and analysis of radiation-sensitive (RAD) mutants that are deficient in this homologous recombination repair... 

Lawrence, C. W., and Christensen, R. B. (1978). Ultraviolet4nduced reversion of cycl alleles in radiation-sensitive strains of yeast. I. revl mutant strains./ Mol Biol 122,1-21. 

The replica-plating method may be used to select many types of mutants for which it would be tedious and inefficient to screen individually. The more common application is to isolate auxotrophic, radiation-sensitive, and conditional-lethal mutants. The so-called conditional-lethal mutants are those which, because they are defective in some manner, survive and grow under permissive conditions but perish under restrictive conditions. 

These restrictive conditions may include /)H, osmotic pressure, and temperature. This class of mutants is well known in microorganisms and insects and may well exist in manunalian cells. Recently, Naha (1969) reported the isolation of four different temperature-sensitive mutants in a hetero-nuclear monkey kidney cell line. In our laboratory, a number of temperature-sensitive mutants have been isolated by the replica-plating procedure (Chu and Smith, unpublished). Mutants sensitive to radiation or other adverse conditions may be similarly isolated and studied. 

Lois R, Buchanan BBN (1994) Severe sensitivity to ultraviolet radiation in an Arabidopsis mutant deficient in flavonoid accumulation II. Mechanisms of UV-resistance in Arabidopsis. Planta 194 504-509... 

Reuber, S., Bornman, J.F., and Weissenbock, G., A flavonoid mutant of barley (Hordeum vulgare L.) exhibits increased sensitivity to LTV-B radiation in the primary leaf, Plant Cell Environ., 19, 593, 1996. 

The radiation response of cells from a GSH-synthetase-deficient patient and its clinically healthy brother are compared in Table 12.22. There, it is seen that the GSH deficiency results in a lower OER both of survival and SSB formation. This is largely due to a reduction of GSH, since the other non-protein sulfhy-dryls (NPSH) are not markedly suppressed in this mutant. The efficiency of GSH has been attributed to its particular spatial distribution, since exogenous thiols (here cysteamine) cannot substitute for this. Other sensitizers such as misonidazole (see below) behave similar as O2 with respect to SSB formation in these two cell lines. 

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