In eukaryotes, a cascade of events named DNA damage response (DDR) has evolved to handle DNA lesions. DDR engages the recruitment of signaling, checkpoint control, repair and chromatin remodeling protein complexes, al...In eukaryotes, a cascade of events named DNA damage response (DDR) has evolved to handle DNA lesions. DDR engages the recruitment of signaling, checkpoint control, repair and chromatin remodeling protein complexes, allowing cell cycle delay, DNA repair or induction of apoptosis. An early DDR event involves the phosphorylation of the histone variant γH2AX on serine 139 (H2AX139 phosphorylation) originating the so-called γH2AX. DDR-related H2AX139 phosphorylation have been extensively studied in interphase nuclei. More recently, γH2AX signals on mitotic chromosomes of asynchronously growing cell cultures were observed. We performed a quantitative analysis of γH2AX signals on γH2AX immunolabeled cytocentrifuged metaphase spreads, analyzing the γH2AX signal distributions of CHO9 chromosomes harboring homologous regions both in control and bleomycin (BLM)-treated cultures. We detected γH2AX signals in CHO9 chromosomes of controls which significantly increase after BLM-exposure. γH2AX signals were uniformly distributed in chromosomes of controls. However, the γH2AX signal distribution in BLM exposed cells was significantly different between chromosomes and among chromosome regions, with few signals near the centromeres and a tendency to increase towards the telomeres. Interestingly, both basal and BLM-induced γH2AX signal distribution were statistically equal between CHO9 homologous chromosome regions. Our results suggest that BLM exerts an effect on H2AX139 phosphorylation, prevailing towards acetylated and gene-rich distal chromosome segments. The comparable H2AX139 phosphorylation of homologous regions puts forward its dependence on chromatin structure or function and its independence of the position in the karyotype.展开更多
组蛋白2A变异体(histone family 2A variant,H2AX)在DNA双链断裂(double-strand break,DSB)损伤时可以发生不同的翻译后修饰,包括磷酸化、乙酰化、甲基化和泛素化。通过这些修饰,H2AX标记损伤的DNA双链,促进局部DNA修复因子和染色体重...组蛋白2A变异体(histone family 2A variant,H2AX)在DNA双链断裂(double-strand break,DSB)损伤时可以发生不同的翻译后修饰,包括磷酸化、乙酰化、甲基化和泛素化。通过这些修饰,H2AX标记损伤的DNA双链,促进局部DNA修复因子和染色体重塑因子的募集,维持基因组的稳定性。这对于DSB的有效修复及细胞周期从周期检查点的恢复都是十分必要的。另外,H2AX在DSB信号通路必不可少的作用及其在肿瘤发生早期被激活事件,使它成为肿瘤生物学研究中的热点基因蛋白。本文中重点阐述近几年H2AX在DSB损伤修复中的研究进展,同时提出将它作为一个表观遗传标记,在人类肿瘤的早期诊断和治疗中的潜在应用价值。展开更多
文摘In eukaryotes, a cascade of events named DNA damage response (DDR) has evolved to handle DNA lesions. DDR engages the recruitment of signaling, checkpoint control, repair and chromatin remodeling protein complexes, allowing cell cycle delay, DNA repair or induction of apoptosis. An early DDR event involves the phosphorylation of the histone variant γH2AX on serine 139 (H2AX139 phosphorylation) originating the so-called γH2AX. DDR-related H2AX139 phosphorylation have been extensively studied in interphase nuclei. More recently, γH2AX signals on mitotic chromosomes of asynchronously growing cell cultures were observed. We performed a quantitative analysis of γH2AX signals on γH2AX immunolabeled cytocentrifuged metaphase spreads, analyzing the γH2AX signal distributions of CHO9 chromosomes harboring homologous regions both in control and bleomycin (BLM)-treated cultures. We detected γH2AX signals in CHO9 chromosomes of controls which significantly increase after BLM-exposure. γH2AX signals were uniformly distributed in chromosomes of controls. However, the γH2AX signal distribution in BLM exposed cells was significantly different between chromosomes and among chromosome regions, with few signals near the centromeres and a tendency to increase towards the telomeres. Interestingly, both basal and BLM-induced γH2AX signal distribution were statistically equal between CHO9 homologous chromosome regions. Our results suggest that BLM exerts an effect on H2AX139 phosphorylation, prevailing towards acetylated and gene-rich distal chromosome segments. The comparable H2AX139 phosphorylation of homologous regions puts forward its dependence on chromatin structure or function and its independence of the position in the karyotype.
文摘组蛋白2A变异体(histone family 2A variant,H2AX)在DNA双链断裂(double-strand break,DSB)损伤时可以发生不同的翻译后修饰,包括磷酸化、乙酰化、甲基化和泛素化。通过这些修饰,H2AX标记损伤的DNA双链,促进局部DNA修复因子和染色体重塑因子的募集,维持基因组的稳定性。这对于DSB的有效修复及细胞周期从周期检查点的恢复都是十分必要的。另外,H2AX在DSB信号通路必不可少的作用及其在肿瘤发生早期被激活事件,使它成为肿瘤生物学研究中的热点基因蛋白。本文中重点阐述近几年H2AX在DSB损伤修复中的研究进展,同时提出将它作为一个表观遗传标记,在人类肿瘤的早期诊断和治疗中的潜在应用价值。
