Lawrence Berkeley National Laboratory, Life Sciences Division, Department of Cancer and DNA Damage Responses, Berkeley, CA 94720, USA.
Int J Radiat Biol. 2011 Jul;87(7):696-710. doi: 10.3109/09553002.2010.549535. Epub 2011 Jan 27.
To investigate γ-H2AX (phosphorylated histone H2AX) and 53BP1 (tumour protein 53 binding protein No. 1) foci formation and removal in proliferating and non-proliferating human mammary epithelial cells (HMEC) after exposure to sparsely and densely ionising radiation under different cell culture conditions.
HMEC cells were grown either as monolayers (2D) or in extracellular matrix to allow the formation of acinar structures in vitro (3D). Foci numbers were quantified by image analysis at various time points after exposure.
Our results reveal that in non-proliferating cells under 2D and 3D cell culture conditions, iron-ion induced γ-H2AX foci were still present at 72 h after exposure, although 53BP1 foci returned to control levels at 48 h. In contrast in proliferating HMEC, both γ-H2AX and 53BP1 foci decreased to control levels during the 24-48 h time interval after irradiation under 2D conditions. Foci numbers decreased faster after γ-ray irradiation and returned to control levels by 12 h regardless of marker, cell proliferation status, and cell culture condition.
The disappearance of radiation-induced γ-H2AX and 53BP1 foci in HMEC has different dynamics that depend on radiation quality and proliferation status. Notably, the general patterns do not depend on the cell culture condition (2D versus 3D). We speculate that the persistent γ-H2AX foci in iron-ion irradiated non-proliferating cells could be due to limited availability of double-strand break (DSB) repair pathways in G0/G1-phase, or that repair of complex DSB requires replication or chromatin remodelling.
研究在不同细胞培养条件下，低剂量和高剂量电离辐射暴露后，增殖和非增殖人乳腺上皮细胞（HMEC）中 γ-H2AX（磷酸化组蛋白 H2AX）和 53BP1（肿瘤蛋白 53 结合蛋白 1 号）焦点的形成和消除。
HMEC 细胞在单层（2D）或细胞外基质中培养，以允许体外形成腺泡结构（3D）。在暴露后不同时间点通过图像分析定量焦点数量。
我们的结果表明，在 2D 和 3D 细胞培养条件下的非增殖细胞中，尽管在 48 小时时 53BP1 焦点恢复到对照水平，但铁离子诱导的 γ-H2AX 焦点在暴露后 72 小时仍然存在。相比之下，在增殖的 HMEC 中，在 2D 条件下照射后 24-48 小时的时间间隔内，γ-H2AX 和 53BP1 焦点均降低至对照水平。无论标记物、细胞增殖状态和细胞培养条件如何，γ 射线照射后焦点数量下降更快，并在 12 小时内恢复至对照水平。
HMEC 中辐射诱导的 γ-H2AX 和 53BP1 焦点的消失具有不同的动力学，这取决于辐射质量和增殖状态。值得注意的是，一般模式不依赖于细胞培养条件（2D 与 3D）。我们推测，铁离子照射的非增殖细胞中持续存在的 γ-H2AX 焦点可能是由于 G0/G1 期双链断裂（DSB）修复途径的有限可用性，或者修复复杂的 DSB 需要复制或染色质重塑。
