THE TRANSCRIPTION OF THE XRCC1 GENE IN SPLEEN FOLLOWING IONIZING IRRADIATION IN RADIOSENSITIVE AND RADIORESISTANT MICE

The XRCC1 gene was described to play a role for the sensitivity of mam malian cell lines towards ionizing irradiation. Cells with a mutation of this gene present with decreased single strand break repair, reduce d recombination repair, show increased double strand breaks and sister chromatid exchange is increased up to tenfold. The goal of our study was to investigate the transcription of this gene in the spleen follow ing ionizing irradiation in the mouse. Furthermore, we intended to exa mine whether radiation sensitive (RS) mice would show a transcriptiona l pattern different from radiation resistant (RR) mice. Radiation sens itive BALB/c/J Him mice and radiation resistant C3H He/Him mice were u ntreated or whole body irradiated with X-ray at 4 and 6 Gy and sacrifi ced 5, 15 and 30 min after irradiation. mRNA was isolated from the spl een and hybridized with probes for XRCC1 and beta-actin as a house kee ping gene control. Transcription of XRCC1 was not different in unirrad iated or 4 Gy irradiated mouse RR or RS mouse strains. When irradiated at 6 Gy, RR mice showed an approximately threefold increase of mRNA X RCC1/mRNA beta actin as early as 15 min after irradiation. We conclude that radiation resistant mice show a higher transcription level for t he XRCC1 gene in the spleen early after high dose X-ray whole body irr adiation. This finding is the first in vivo study on XRCC1 of this kin d and may in part explain the differences in the radiation sensitivity between the two strains studied.