Study of uv-mutagenesis in Bacillus subtilis. II. Restoration of biological activity of cellular DNA in conditions determining different sensitivity of cells to the mutagenic action of ultraviolet light

Journal Article · Mon Oct 01 04:00:00 EDT 1973 · Genetika, v. 9, no. 10, pp. 97-105

OSTI ID:4338966

Filippov, V D; Lekevichus, E K

The frequency of uv-induced revertants to adenine (Ade) or methionine (Met) prototrophy as well as the frequency of double revertants (Ade Met), determined by one mutation, decreased in Bacillus subtilis cells irradiated in exponential phase, if they were subsequently incubated without nitrogen sources or with chloramphenlcol (CA), and still more in the cells of stationary phase. The measurement of transforming activity (TA) of the ade6 and met5 markers of cellular DNA in the irradiated bacteria of isogenic prototroph strains provided the following results. Soon after irradiation the restoration of TA was observed in the cells of exponential phase incubated in nutritional medium. The rate of restoration decreased when incubation proceeded in a medium deprived of nitrogen sources or with CA. The long delay of the TA restoration can be seen in irradiated cells of the stationary phase. It is suggested on the basis of these data that a process, which depends on protein synthesis and provides a rapid restoration of TA of damaged cellular DNA, has mutagenic activity in Bac. subtilis. The nature of this process is under study in this laboratory. The low frequency of induced mutations in the cells of the of protein synthesis in these cells. (auth) O H15869 The action of an endonuclease from Micrococcus luteus, that operates on ultraviolet(uv) radiation damage, overlaps greatly with that of the yeast photoreactivating euzyme: homo and hetero cyclobutylpyrimidine dimers in DNA are substrate for both enzymes, but pyrimidine adducts or the spore photoproduct'' in DNA are not. As expectcd from this overlap, the action of the two enzymes was mutually interfering: single-strand nicks introduced by the endonuclease effectively precluded photoreactivation: conversely, formation of a photoreactivating exzyme-dimer complex prevented nicking by the uv endonuclease. While complex formation between photoreactivating enzyme and dimers in uvendonuclease-treated DNA was apparently normal, the lightdependent repair step either failed to occur or proceeded at a very low rate. Hence, besides the requirement of a minimum chain length for the function of the photoreactivating enzyme, there was the additional restriction on the position of the dimer in a polynucleotide strand. Rough approximations of the rate constants, k/sub 1/ and k/sub 2/, for the uv endonuclease indicated that the in vitro uvendonuclease- dimer complex is relatively unstable, with dissociation of the complex being more probable than hydrolysis of the phosphodiester bond. (auth)

• Research Organization: Inst. of General Genetics, Moscow
• NSA Number: NSA-29-015868
• OSTI ID: 4338966
• Journal Information: Genetika, v. 9, no. 10, pp. 97-105, Journal Name: Genetika, v. 9, no. 10, pp. 97-105; ISSN GNKAA
• Country of Publication: Country unknown/Code not available
• Language: Russian

Related Subjects

*BACILLUS SUBTILIS-- MUTATIONS
*DNA-- BIOLOGICAL REPAIR
*MUTATIONS-- RADIOINDUCTION
BIOLOGICAL RADIATION EFFECTS
BIOSYNTHESIS
CHLORAMPHENICOL
MUTAGENESIS
MUTATION FREQUENCY
N48310* --Life Sciences--Radiation Effects on Microorganisms- -Basic Studies
NITROGEN
PHOTON BEAMS
PROTEINS
ULTRAVIOLET RADIATION