染色体切断の修復は細胞の低線量/低線量率γ線照射による影響を受ける

摘要

DSB was introduced by the I-Sce I expression vector, pCMV3xnls-I-Sce I. Repair of DSB at the I-Scel site inserted at intron 4 of the tk+ allele in human lymphoblstoid TK6 cell line, TSCE5, was measured by induction of TK-deficient mutants. Similarly we also measured the revertants due to such repair in its compound heterozygote (tk-/-) cell line, TSCER2, which carried an additional point-mutation in exon 5. The former and later measurements reflect the DSB repair efficiency due to DNA end-joining (EJ) and homologous recombination (HR), respectively. The pre-treatment,y-irradiation with 30 mGy at a dose rate of1.2 mGy/hr did not influence the EJ repair efficiency but enhanced HR repair efficiency,～50 ％. The I-Scel digestion followed by much lower dose(/dose-rate) y-irradiation (8.5 mGy at 0.125 mGy/hr) during the incubation tesulted in a similar tendency of HR enhancement(～50 ％). This kind of treatment, introducing the chromosome break by the restriction enzyme, can be regarded as a useful approach for elucidating the influences of space environments on the DSB repair.%ふつう、宇宙環境は微小重力に象徴されている。低線量かつ低線量率の宇宙放射線による被ばくの影響も見逃してはならないと思われる。これらの問題は、単に宇宙飛行士への健康影響といった観点からだけではなく、もう少し将来を見据えた宇宙環境利用といった大きな視野からも検討が必要な問題であろう。重力影響と放射線の影響を切り離して評価する系の樹立も望ましく、これらの相乗効果の存在までも評価できるともっとよい。