RESUMO
Two cell repair systems--photoreactivation and repair of single-strand DNA breaks have been studied using unicellular green algae as a test-system. Effects of the genotype and the intensity of pico/second UV-laser irradiation on the degree of the photoreactivation have been investigated. It has been shown that the lower intensity (I = 8.10(6) W/cm2) effects less the inactivation of living cells comparing with I = 30.10(6) W/cm2, regardless of the genotype. The clearly expressed higher potentials of strains LARG-1 and 260 to produce and repair alterations of the cyclobutane-pyrimidine dimers type have been established. An analysis of DNA degradation during gamma rays irradiation and after incubation has been carried out for investigation the relationship between strains radioresistance and repair of single-strand break. It has been shown that high efficiency of the repair system is characteristic of the resistant strain obtained from chronically irradiated population.
Assuntos
Chlorella/efeitos da radiação , Reparo do DNA , Chlorella/genética , Chlorella/metabolismo , DNA/metabolismo , DNA/efeitos da radiação , Dano ao DNA , Reparo do DNA/efeitos da radiação , Raios gama , Genótipo , Luz , Tolerância a Radiação , Raios UltravioletaRESUMO
A picosecond UV laser was used to cross-link proteins to DNA in nuclei, whole cells and reconstituted nucleohistone. Irradiation of the nucleohistone resulted in crosslinking 15-20% of bound histones to DNA in a very short time (one or several picosecond pulses), the efficiency of crosslinking to single stranded DNA being higher than to double stranded DNA. All histones as well as high mobility group 1 proteins were identified in the covalently linked protein-DNA complexes upon irradiation of isolated nuclei and whole cells. A method is suggested for isolation of crosslinked material from cells and nuclei in amounts sufficient for further analysis. Experiments with reconstituted nucleohistones showed that upon irradiation at a constant dose the efficiency of crosslinking depended on the intensity of the light, thus suggesting a two-quantum process is involved in the reaction.