St. Vincent's Institute of Medical Research, Fitzroy, Australia.
PLoS Genet. 2010 Oct 21;6(10):e1001170. doi: 10.1371/journal.pgen.1001170.
Zn²(+)-finger proteins comprise one of the largest protein superfamilies with diverse biological functions. The ATM substrate Chk2-interacting Zn²(+)-finger protein (ASCIZ; also known as ATMIN and ZNF822) was originally linked to functions in the DNA base damage response and has also been proposed to be an essential cofactor of the ATM kinase. Here we show that absence of ASCIZ leads to p53-independent late-embryonic lethality in mice. Asciz-deficient primary fibroblasts exhibit increased sensitivity to DNA base damaging agents MMS and H2O2, but Asciz deletion knock-down does not affect ATM levels and activation in mouse, chicken, or human cells. Unexpectedly, Asciz-deficient embryos also exhibit severe respiratory tract defects with complete pulmonary agenesis and severe tracheal atresia. Nkx2.1-expressing respiratory precursors are still specified in the absence of ASCIZ, but fail to segregate properly within the ventral foregut, and as a consequence lung buds never form and separation of the trachea from the oesophagus stalls early. Comparison of phenotypes suggests that ASCIZ functions between Wnt2-2b/ß-catenin and FGF10/FGF-receptor 2b signaling pathways in the mesodermal/endodermal crosstalk regulating early respiratory development. We also find that ASCIZ can activate expression of reporter genes via its SQ/TQ-cluster domain in vitro, suggesting that it may exert its developmental functions as a transcription factor. Altogether, the data indicate that, in addition to its role in the DNA base damage response, ASCIZ has separate developmental functions as an essential regulator of respiratory organogenesis.
Zn²(+)-finger 蛋白构成了最大的蛋白质超家族之一，具有多种生物学功能。ATM 底物 Chk2 相互作用的 Zn²(+)-finger 蛋白（ASCIZ；也称为 ATMIN 和 ZNF822）最初与 DNA 碱基损伤反应的功能有关，也被提议为 ATM 激酶的必需辅助因子。在这里，我们表明 ASCIZ 的缺失会导致小鼠出现无 p53 的晚期胚胎致死。缺乏 ASCIZ 的原代成纤维细胞对 DNA 碱基损伤剂 MMS 和 H2O2 表现出更高的敏感性，但 ASCIZ 缺失敲低不会影响 ATM 水平和小鼠、鸡或人细胞中的激活。出乎意料的是，缺乏 ASCIZ 的胚胎也表现出严重的呼吸道缺陷，完全肺发育不全和严重的气管闭锁。在缺乏 ASCIZ 的情况下，NKX2.1 表达的呼吸前体细胞仍然被指定，但不能在腹侧前肠内正确分离，因此肺芽从未形成，气管与食管的分离很早就停止了。表型比较表明，ASCIZ 在线粒体 Wnt2-2b/β-连环蛋白和 FGF10/FGF-受体 2b 信号通路之间的功能在调节早期呼吸发育的中胚层/内胚层串扰中起作用。我们还发现 ASCIZ 可以在体外通过其 SQ/TQ-簇结构域激活报告基因的表达，表明它可能作为转录因子发挥其发育功能。总之，这些数据表明，除了在 DNA 碱基损伤反应中的作用外，ASCIZ 作为呼吸器官发生的必需调节剂具有独立的发育功能。
