Carbone Roberta, Pearson Mark, Minucci Saverio, Pelicci Pier Giuseppe
Department of Experimental Oncology, European Institute of Oncology, Via Ripamonti 435, 20141 Milan, Italy.
Oncogene. 2002 Mar 7;21(11):1633-40. doi: 10.1038/sj.onc.1205227.
PML nuclear bodies (PML NBs) respond to many cellular stresses including viral infection, heat shock, arsenic and oncogenes and have been implicated in the regulation of p53-dependent replicative senescence and apoptosis. Recently, the hMre11/Rad50/NBS1 repair complex, involved in Double Strand Breaks (DSBs) repair, was found to colocalize within PML NBs, suggesting a role for these nuclear sub-domains in the DNA repair signalling pathway. We report here that in normal human fibroblasts, after ionizing radiation (IR), the PML NBs are modified and recognize sites of DNA breaks (ssDNA breaks and DSBs). Eight to 12 h after radiation PML NBs associate with hMre11 Ionizing Radiation-Induced Foci (IRIF), and subsequently with p53 within discrete foci. The PML, hMre11 and p53 colocalizing structures mark sites of DSBs as identified by immunolocalization with anti phosphorylated histone gamma-H2AX. Furthermore, we demonstrate that ionizing radiation induces the stable association of p53 with hMre11 and PML. These results suggest that the PML NBs are involved in the recognition and/or processing of DNA breaks and possibly in the recruitment of proteins (p53 and hMre11) required for both checkpoint and DNA-repair responses.
早幼粒细胞白血病核小体（PML核小体）对包括病毒感染、热休克、砷和癌基因在内的多种细胞应激作出反应，并参与了p53依赖的复制性衰老和凋亡的调控。最近，参与双链断裂（DSB）修复的hMre11/Rad50/NBS1修复复合物被发现与PML核小体共定位，这表明这些核亚结构域在DNA修复信号通路中发挥作用。我们在此报告，在正常人成纤维细胞中，电离辐射（IR）后，PML核小体发生改变并识别DNA断裂位点（单链DNA断裂和双链断裂）。辐射后8至12小时，PML核小体与hMre11电离辐射诱导灶（IRIF）相关联，随后在离散的灶中与p53相关联。通过用抗磷酸化组蛋白γ-H2AX进行免疫定位鉴定，PML、hMre11和p53共定位结构标记了双链断裂位点。此外，我们证明电离辐射诱导p53与hMre11和PML稳定结合。这些结果表明，PML核小体参与DNA断裂的识别和/或处理，可能还参与募集检查点和DNA修复反应所需的蛋白质（p53和hMre11）。
