de Klein A, Muijtjens M, van Os R, Verhoeven Y, Smit B, Carr A M, Lehmann A R, Hoeijmakers J H
MGC Department of Cell Biology and Genetics, Center for Biomedical Genetics, Erasmus University, Rotterdam, The Netherlands.
Curr Biol. 2000 Apr 20;10(8):479-82. doi: 10.1016/s0960-9822(00)00447-4.
Checkpoints of DNA integrity are conserved throughout evolution, as are the kinases ATM (Ataxia Telangiectasia mutated) and ATR (Ataxia- and Rad-related), which are related to phosphatidylinositol (PI) 3-kinase [1] [2] [3]. The ATM gene is not essential, but mutations lead to ataxia telangiectasia (AT), a pleiotropic disorder characterised by radiation sensitivity and cellular checkpoint defects in response to ionising radiation [4] [5] [6]. The ATR gene has not been associated with human syndromes and, structurally, is more closely related to the canonical yeast checkpoint genes rad3(Sp) and MEC1(Sc) [7] [8]. ATR has been implicated in the response to ultraviolet (UV) radiation and blocks to DNA synthesis [8] [9] [10] [11], and may phosphorylate p53 [12] [13], suggesting that ATM and ATR may have similar and, perhaps, complementary roles in cell-cycle control after DNA damage. Here, we report that targeted inactivation of ATR in mice by disruption of the kinase domain leads to early embryonic lethality before embryonic day 8.5 (E8.5). Heterozygous mice were fertile and had no aberrant phenotype, despite a lower ATR mRNA level. No increase was observed in the sensitivity of ATR(+/-) embryonic stem (ES) cells to a variety of DNA-damaging agents. Attempts to target the remaining wild-type ATR allele in heterozygous ATR(+/-) ES cells failed, supporting the idea that loss of both alleles of the ATR gene, even at the ES-cell level, is lethal. Thus, in contrast to the closely related checkpoint gene ATM, ATR has an essential function in early mammalian development.
DNA完整性检查点在整个进化过程中都得以保留，与磷脂酰肌醇（PI）3激酶相关的共济失调毛细血管扩张症突变激酶（ATM）和共济失调与Rad相关激酶（ATR）也是如此[1][2][3]。ATM基因并非必需基因，但突变会导致共济失调毛细血管扩张症（AT），这是一种多效性疾病，其特征为对辐射敏感以及对电离辐射产生细胞检查点缺陷[4][5][6]。ATR基因尚未与人类综合征相关联，并且在结构上与典型的酵母检查点基因rad3（Sp）和MEC1（Sc）更为密切相关[7][8]。ATR与对紫外线（UV）辐射的反应以及DNA合成受阻有关[8][9][10][11]，并且可能使p53磷酸化[12][13]，这表明ATM和ATR在DNA损伤后的细胞周期控制中可能具有相似甚至互补的作用。在此，我们报道通过破坏激酶结构域在小鼠中靶向灭活ATR会导致在胚胎第8.5天（E8.5）之前出现早期胚胎致死性。杂合小鼠可育且无异常表型，尽管ATR mRNA水平较低。未观察到ATR（+/-）胚胎干细胞（ES）对多种DNA损伤剂的敏感性增加。在杂合ATR（+/-）ES细胞中靶向剩余野生型ATR等位基因的尝试失败了，这支持了即使在ES细胞水平，ATR基因两个等位基因的缺失也是致死的这一观点。因此，与密切相关的检查点基因ATM不同，ATR在早期哺乳动物发育中具有重要功能。
