A minority of foci or pan-nuclear apoptotic staining of γH2AX in the S phase after UV damage contain DNA double-strand breaks
A minority of foci or pan-nuclear apoptotic staining of γH2AX in the S phase after UV damage contain DNA double-strand breaks
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DOI：
10.1073/pnas.1002175107
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发表时间：
2010-04-13
影响因子：
11.1
通讯作者：
Cleaver, James E.
中科院分区：
文献类型：
--
作者：
de Feraudy, Sebastien;Revet, Ingrid;Cleaver, James E.
紫外线照射诱导组蛋白变体H2 AX磷酸化丝氨酸139（γ H2 AX）焦点和高水平的泛核γ H2 AX染色无焦点，但这一发现的意义仍然不确定。我们研究了电离辐射后在双链断裂（DSB）位点重合的γ H2 AX和53 BP 1的形成。我们比较了紫外线照射和依托泊苷治疗，依托泊苷是一种在DNA复制过程中引起DSB的药物。我们发现，在DNA复制过程中，紫外线照射诱导至少三类γ H2 AX反应：少数γ H2 AX焦点与代表复制位点处DSB的53 BP 1焦点共定位，大多数γ H2 AX焦点不与53 BP 1焦点共定位，以及具有高水平的全核γ H2 AX而没有γ H2 AX或53 BP 1焦点的细胞。共济失调-毛细血管扩张突变激酶和JNK介导了紫外线诱导的泛核γ H2 Ax，其先于并抑制紫外线诱导的S期细胞凋亡。这些高水平的泛核γ H2 AX进一步增加的旁路聚合酶Pol eta和共济失调毛细血管扩张和Rad 3相关的抑制的损失，但水平需要切除修复着色性干皮病互补组A和C蛋白的损伤结合蛋白的存在。因此，DSB代表了一个小的可变部分的UV诱导的γ H2 AX焦点依赖于修复能力，他们没有检测到高水平的泛核γ H2 AX，与ATM-和JNK-依赖性细胞凋亡在复制过程中的凋亡前信号。因此，在没有独立的确证证据的情况下，用DNA损伤剂治疗后γ H2 AX病灶的形成不能用作DSB的直接测量。
UV irradiation induces histone variant H2AX phosphorylated on serine 139 (gamma H2AX) foci and highlevels of pan-nuclear gamma H2AX staining without foci, but the significance of this finding is still uncertain. We examined the formation of gamma H2AX and 53BP1 that coincide at sites of double-strand breaks (DSBs) after ionizing radiation. We compared UV irradiation and treatment with etoposide, an agent that causes DSBs during DNA replication. We found that during DNA replication, UV irradiation induced at least three classes of gamma H2AX response: a minority of gamma H2AX foci colocalizing with 53BP1 foci that represent DSBs at replication sites, a majority of gamma H2AX foci that did not colocalize with 53BP1 foci, and cells with high levels of pan-nuclear gamma H2AX without foci of either gamma H2AX or 53BP1. Ataxia-telangiectasia mutated kinase and JNK mediated the UV-induced pan-nuclear gamma H2Ax, which preceded and paralleled UV-induced S phase apoptosis. These high levels of pan-nuclear gamma H2AX were further increased by loss of the bypass polymerase Pol eta and inhibition of ataxia-telangiectasia and Rad3-related, but the levels required the presence of the damage-binding proteins of excision repair xeroderma pigmentosum complementation group A and C proteins. DSBs, therefore, represent a small variable fraction of UV-induced gamma H2AX foci dependent on repair capacity, and they are not detected within high levels of pan-nuclear gamma H2AX, a preapoptotic signal associated with ATM- and JNK-dependent apoptosis during replication. The formation of gamma H2AX foci after treatment with DNA-damaging agents cannot, therefore, be used as a direct measure of DSBs without independent corroborating evidence.