Cremer C, Cremer T, Hens L, Baumann H, Cornelis J J, Nakanishi K
Mutat Res. 1983 Feb;107(2):465-76. doi: 10.1016/0027-5107(83)90184-7.
UV micro-irradiation of a small part of the Chinese hamster nucleus and caffeine post-incubation often results in shattered chromosomes at the first post-irradiation mitosis. In some of these mitotic cells, chromosome shattering is restricted to a few chromosomes spatially related in a small area of the metaphase spread; in others, shattering includes the whole chromosome complement. These 2 types of damage have been called partial and generalized chromosome shattering (PCS and GCS). Using antisera that specifically react with UV-irradiated DNA, we identified micro-irradiated chromatin in interphase nuclei and in mitotic cells with PCS or GCS by indirect immunofluorescence microscopy. In PCS, immunofluorescence staining was found in the damaged area, while the surrounding intact chromosomes were not stained. In GCS, staining was also restricted to a small region of the shattered chromosome complement. In other experiments, cells synchronized in G1 were micro-irradiated in the nucleus, pulse-labelled with [3H]thymidine and post-incubated with caffeine. Autoradiographs of cells with GCS showed unscheduled DNA synthesis restricted to a small chromatin region. Our data present direct evidence that the distribution of DNA photolesions does not coincide with the sites of chromosomal damage in GCS. As a working, hypothesis, we propose that an indirect mechanism is involved in the induction of GCS by which DNA photolesions in a small nuclear segment induce shattering of both micro-irradiated and non-irradiated chromosomes.
对中国仓鼠细胞核的一小部分进行紫外线微照射并在照射后用咖啡因孵育，常常会导致在首次照射后有丝分裂时染色体破碎。在其中一些有丝分裂细胞中，染色体破碎仅限于中期铺展中小区域内空间相关的少数几条染色体；在另一些细胞中，破碎则包括整个染色体组。这两种类型的损伤分别被称为局部染色体破碎和全身性染色体破碎（PCS和GCS）。使用能与紫外线照射的DNA特异性反应的抗血清，我们通过间接免疫荧光显微镜在间期核以及有PCS或GCS的有丝分裂细胞中鉴定出了微照射的染色质。在PCS中，在损伤区域发现了免疫荧光染色，而周围完整的染色体未被染色。在GCS中，染色也局限于破碎染色体组的一个小区域。在其他实验中，将处于G1期同步化的细胞在细胞核中进行微照射，用[3H]胸腺嘧啶脉冲标记，然后用咖啡因孵育。有GCS的细胞的放射自显影片显示，DNA的非预定合成局限于一个小的染色质区域。我们的数据提供了直接证据，表明在GCS中DNA光损伤的分布与染色体损伤的位点不一致。作为一个可行的假设，我们提出一种间接机制参与了GCS的诱导，即小核段中的DNA光损伤诱导微照射和未照射染色体的破碎。
