Division of Hematology-Oncology, Department of Pediatrics, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd. MC 9063, Dallas, TX 75390, USA.
Dev Biol. 2013 Aug 1;380(1):49-57. doi: 10.1016/j.ydbio.2013.05.003. Epub 2013 May 9.
The Arf tumor suppressor represents one of several genes encoded at the Cdkn2a and Cdkn2b loci in the mouse. Beyond its role blunting the growth of incipient cancer cells, the Arf gene also plays an essential role in development: its gene product, p19(Arf), is induced by Tgfβ2 in the developing eye to dampen proliferative signals from Pdgfrβ, which effect ultimately fosters the vascular remodeling required for normal vision in the mouse. Mechanisms underlying Arf induction by Tgfβ2 are not fully understood. Using the chr4(Δ70 kb/Δ70 kb) mouse, we now show that deletion of the coronary artery disease (CAD) risk interval lying upstream of the Cdkn2a/b locus represses developmentally-timed induction of Arf resulting in eye disease mimicking the persistent hyperplastic primary vitreous (PHPV) found in Arf-null mice and in children. Using mouse embryo fibroblasts, we demonstrate that Arf induction by Tgfβ is blocked in cis to the 70 kb deletion, but Arf induction by activated RAS and cell culture "shock" is not. Finally, we show that Arf induction by Tgfβ is derailed by preventing RNA polymerase II recruitment following Smad 2/3 binding to the promoter. These findings provide the first evidence that the CAD risk interval, located at a distance from Arf, acts as a cis enhancer of Tgfβ2-driven induction of Arf during development.
Arf 肿瘤抑制因子代表了小鼠 Cdkn2a 和 Cdkn2b 基因座编码的几个基因之一。除了在削弱初始癌细胞生长方面的作用外，Arf 基因在发育中也起着至关重要的作用：其基因产物 p19(Arf)，在发育中的眼睛中被 Tgfβ2 诱导，以抑制来自 Pdgfrβ 的增殖信号，最终促进了小鼠正常视力所需的血管重塑。Tgfβ2 诱导 Arf 的机制尚未完全了解。我们使用 chr4(Δ70 kb/Δ70 kb) 小鼠，现在表明，位于 Cdkn2a/b 基因座上游的冠心病 (CAD) 风险间隔缺失会抑制 Arf 的发育性诱导，导致眼部疾病类似于在 Arf 缺失小鼠和儿童中发现的持续性增生性原始玻璃体 (PHPV)。使用小鼠胚胎成纤维细胞，我们证明 Tgfβ 诱导的 Arf 在顺式到 70 kb 缺失处被阻断，但激活的 RAS 和细胞培养“休克”诱导的 Arf 不受影响。最后，我们表明，Tgfβ 诱导的 Arf 诱导被阻止，方法是在 Smad 2/3 结合到启动子后阻止 RNA 聚合酶 II 的募集。这些发现提供了第一个证据，表明位于 Arf 远处的 CAD 风险间隔作为 Tgfβ2 驱动的发育中 Arf 诱导的顺式增强子。
