Bhakat Kishor K, Izumi Tadahide, Yang Suk-Hoon, Hazra Tapas K, Mitra Sankar
Sealy Center for Molecular Science and Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, TX 77555-1079, USA.
EMBO J. 2003 Dec 1;22(23):6299-309. doi: 10.1093/emboj/cdg595.
The human AP-endonuclease (APE1/Ref-1), a multifunctional protein central to repairing abasic sites and single-strand breaks in DNA, also plays a role in transcriptional regulation. Besides activating some transcription factors, APE1 is directly involved in Ca2+-dependent downregulation of parathyroid hormone (PTH) expression by binding to negative calcium response elements (nCaREs) present in the PTH promoter. Here we show that APE1 is acetylated both in vivo and in vitro by the transcriptional co-activator p300 which is activated by Ca2+. Acetylation at Lys6 or Lys7 enhances binding of APE1 to nCaRE. APE1 stably interacts with class I histone deacetylases (HDACs) in vivo. An increase in extracellular calcium enhances the level of acetylated APE1 which acts as a repressor for the PTH promoter. Moreover, chromatin immunoprecipitation (ChIP) assay revealed that acetylation of APE1 enhanced binding of the APE1-HDACs complex to the PTH promoter. These results indicate that acetylation of APE1 plays an important role in this key repair protein's action in transcriptional regulation.
人脱嘌呤嘧啶内切核酸酶（APE1/Ref-1）是一种多功能蛋白质，在修复DNA中的无碱基位点和单链断裂方面起着核心作用，同时也参与转录调控。除了激活一些转录因子外，APE1还通过与甲状旁腺激素（PTH）启动子中存在的负钙反应元件（nCaREs）结合，直接参与Ca2+依赖性的PTH表达下调。在此我们表明，转录共激活因子p300在体内和体外均可使APE1乙酰化，而p300可被Ca2+激活。赖氨酸6或赖氨酸7处的乙酰化增强了APE1与nCaRE的结合。APE1在体内与I类组蛋白去乙酰化酶（HDACs）稳定相互作用。细胞外钙的增加会提高乙酰化APE1的水平，而乙酰化APE1可作为PTH启动子的抑制因子。此外，染色质免疫沉淀（ChIP）分析表明，APE1的乙酰化增强了APE1-HDACs复合物与PTH启动子的结合。这些结果表明，APE1的乙酰化在这种关键修复蛋白的转录调控作用中起着重要作用。
