Induction and repair of DNA double-strand breaks under irradiation and microgravity

The influence of microgravity on induction and repair of double-strand brea ks was studied in the yeast mutant rad54-3, which is temperature-conditiona l for the repair of DNA double-strand breaks. The experiment was performed on the shuttle Atlantis flight STS-84, Cell samples were kept at 0-4 degree s C until they reached orbit, where they were transferred to 22 (permissive temperature for repair) and 37 degrees C (restrictive temperature). They w ere exposed to graded doses of beta particles from an inbuilt Ni-63 source during the repair period. After 152 h in microgravity, the radiation exposu re was stopped, and the samples were returned to low-temperature conditions , where they remained until final evaluation in the home laboratory. The am ount of double-strand breaks remaining was estimated from the differences i n survival after plating and incubation at the restrictive temperature. The results show that there is no significant difference for both the inductio n and the repair of double-strand breaks between microgravity and terrestri al conditions. (C) 2000 by Radiation Research Society.