45S rDNA基因由串联重复序列构成, 是遗传不稳定性的热点区域, 易于发生DNA断裂和重组。以Hela和CHO细胞系为研究对象, 运用荧光原位杂交技术检测有丝分裂不同时期的45S rDNA基因的不稳定性表型。结果表明, 位点特异性的染色体浓缩失败是其在中期染色体上不稳定性的主要表型。具有这种表型的染色体在后期可能会出现落后或粘连现象, 甚至有可能引发断裂, 形成卫星核。同时, 免疫荧光双染色技术检测表明DNA双链断裂的标记蛋白(γH2AX)和RNA聚合酶I的上游结合因子(UBF)在有丝分裂的不同时期都存在共定位现象。该结果为探讨45S rDNA基因的不稳定性与转录的关系提供了直观的细胞学证据。

45S rDNA gene, which is composed of tandem repeats, is a hot spot of genetic instability and prone to DNA breakage and recombination. Taking Hela and CHO cell lines as a subject to be investigated, the instability phenotype of 45S rDNA gene in different mitotic stages was detected by fluorescence in situ hybridization. The results showed that the site-specific chromosome condensation failure was the main instability phenotype in metaphase chromosomes. The chromosome with the phenotype might delay or adhere in anaphase, and might even cause breakage to form a micronucleus. Meanwhile, the colocalization of the DNA double strand break marker (γH2AX) with the upstream binding factor (UBF) of RNA polymerase I in different mitotic stages was detected by immunofluorescence double staining technique. The results provided an intuitive cytological evidence for the study of the relationship between the instability of 45S rDNA gene and transcription.