Cartwright Ian M, Kato Takamitsu A
a Department of Environmental and Radiological Health Sciences , Colorado State University , Fort Collins , USA.
Int J Radiat Biol. 2015;91(12):925-33. doi: 10.3109/09553002.2015.1101499. Epub 2015 Oct 29.
In an effort to better understand the formation of chromosomal inversions, we investigated the role of various DNA repair pathways, including the non-homologous end joining (NHEJ), homologous recombination (HR), and Fanconi Anemia (FA) repair pathways for the formation of radiation induced chromosomal inversions.
CHO10B2 wild type, CHO DNA repair-deficient, and CHO DNA repair-deficient corrected mutant cells were synchronized into G1 phase and exposed to gamma-rays. First post-irradiation metaphase cells were analyzed for chromosomal inversions by a differential chromatid staining technique involving a single cycle pre-irradiation ethynyl-uridine treatment and statistic calculations.
It was observed that inhibition of the NHEJ pathway resulted in an overall decrease in the number of radiation-induced inversions, roughly a 50% decrease when compared to the CHO wild type. Interestingly, inhibition of the FA pathway resulted in an increase in both the number of spontaneous inversions and the number of radiation-induced inversions observed after exposure to 2 Gy of ionizing radiation. It was observed that FA-deficient cells contained roughly 330% (1.24 inversions per cell) more spontaneous inversions and 20% (0.4 inversions per cell) more radiation-induced inversions than the wild-type CHO cell lines. The HR mutants, defective in Rad51 foci, showed similar number of spontaneous and radiation-induced inversion as the wild-type cells. Gene complementation resulted in both spontaneous and radiation-induced inversions resembling the CHO wild-type cells.
We have concluded that the NHEJ repair pathway contributes to the formation of radiation-induced inversions. Additionally, through an unknown molecular mechanism it appears that the FA signal pathway prevents the formation of both spontaneous and radiation induced inversions.
为了更好地理解染色体倒位的形成，我们研究了各种DNA修复途径的作用，包括非同源末端连接（NHEJ）、同源重组（HR）和范可尼贫血（FA）修复途径在辐射诱导的染色体倒位形成中的作用。
将CHO10B2野生型、CHO DNA修复缺陷型和CHO DNA修复缺陷校正突变细胞同步到G1期，然后暴露于γ射线。通过一种差异染色单体染色技术分析首次照射后中期细胞的染色体倒位情况，该技术涉及单次照射前乙炔基尿苷处理和统计计算。
观察到抑制NHEJ途径导致辐射诱导倒位的数量总体减少，与CHO野生型相比大致减少50%。有趣的是，抑制FA途径导致自发倒位的数量以及暴露于2 Gy电离辐射后观察到的辐射诱导倒位的数量增加。观察到FA缺陷细胞的自发倒位比野生型CHO细胞系多约330%（每个细胞1.24个倒位），辐射诱导倒位多20%（每个细胞0.4个倒位）。Rad51焦点缺陷的HR突变体显示出与野生型细胞相似数量的自发和辐射诱导倒位。基因互补导致自发和辐射诱导倒位类似于CHO野生型细胞。
我们得出结论，NHEJ修复途径有助于辐射诱导倒位的形成。此外，通过未知的分子机制，FA信号通路似乎阻止了自发和辐射诱导倒位的形成。
