Li Mengxia, Dai Nan, Wang Dong, Zhong Zhaoyang
Cancer Center, The Third Affiliated Hospital and Research Institute of Surgery of Army Medical University (Third Military Medical University), Chongqing 400042, PR China.
Comput Struct Biotechnol J. 2019 Feb 21;17:324-332. doi: 10.1016/j.csbj.2019.02.007. eCollection 2019.
Angiogenesis is essential for tumor growth. Vascular endothelial growth factor (VEGF), a crucial factor in tumor angiogenesis, has been reported to be transcriptionally regulated by hypoxia-inducible factor-1 (HIF-1). An 8-oxo-G or apurinic/apyrimidinic (AP) site, which is frequently associated with DNA damage, has been identified in the promoter region of VEGF. However, the detailed molecular mechanisms by which AP sites regulate VEGF gene transcription are largely unknown. The dual functional protein apurinic/apyrimidinic endonuclease 1 (APE1) is both the key enzyme in DNA base excision repair and the redox factor shown to regulate HIF-1 DNA-binding activity. In the present study, we tested the involvement of both the AP endonuclease and redox activity of APE1 in regulating HIF-1 DNA binding and VEGF transcription in HUVECs. By employing two APE1 activity-specific inhibitors and AP-site-containing reporter constructs, we confirmed that both activities of APE1 were involved in regulating VEGF expression under hypoxic conditions. Furthermore, we found that the interaction between APE1 and its downstream repair enzyme, DNA polymerase β, was compromised when the N-terminal structure of APE1 was distorted under oxidative conditions. Our data suggest that the DNA repair and redox activity of APE1 can play a collaborative role in regulating the transcriptional initiation of the AP-site-containing promoter.
血管生成对肿瘤生长至关重要。血管内皮生长因子（VEGF）是肿瘤血管生成中的关键因子，据报道其受缺氧诱导因子-1（HIF-1）的转录调控。在VEGF的启动子区域已鉴定出一个8-氧代鸟嘌呤（8-oxo-G）或无嘌呤/无嘧啶（AP）位点，该位点常与DNA损伤相关。然而，AP位点调控VEGF基因转录的详细分子机制在很大程度上尚不清楚。双功能蛋白无嘌呤/无嘧啶内切核酸酶1（APE1）既是DNA碱基切除修复中的关键酶，也是显示可调节HIF-1 DNA结合活性的氧化还原因子。在本研究中，我们测试了APE1的AP内切核酸酶活性和氧化还原活性在调节人脐静脉内皮细胞（HUVECs）中HIF-1 DNA结合和VEGF转录方面的作用。通过使用两种APE1活性特异性抑制剂和含AP位点的报告基因构建体，我们证实了APE1的两种活性均参与缺氧条件下VEGF表达的调节。此外，我们发现当APE1的N端结构在氧化条件下扭曲时，APE1与其下游修复酶DNA聚合酶β之间的相互作用受到损害。我们的数据表明，APE1的DNA修复和氧化还原活性在调节含AP位点启动子的转录起始中可发挥协同作用。
