Department of Pharmacology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53706, USA.
Mol Cell. 2012 Jan 13;45(1):25-37. doi: 10.1016/j.molcel.2011.11.017.
BIK protein is an initiator of mitochondrial apoptosis, and BIK expression is induced by proapoptotic signals, including DNA damage. Here, we demonstrate that 3' end processing and expression of BIK mRNA are controlled by the nuclear PI4,5P(2)-regulated poly(A) polymerase Star-PAP downstream of DNA damage. Nuclear PKCδ is a key mediator of apoptosis, and DNA damage stimulates PKCδ association with the Star-PAP complex where PKCδ is required for Star-PAP-dependent BIK expression. PKCδ binds the PI4,5P(2)-generating enzyme PIPKIα, which is essential for PKCδ interaction with the Star-PAP complex, and PKCδ activity is directly stimulated by PI4,5P(2). Features in the BIK 3' UTR uniquely define Star-PAP specificity and may block canonical PAP activity toward BIK mRNA. This reveals a nuclear phosphoinositide signaling nexus where PIPKIα, PI4,5P(2), and PKCδ regulate Star-PAP control of BIK expression and induction of apoptosis. This pathway is distinct from the Star-PAP-mediated oxidative stress pathway indicating signal-specific regulation of mRNA 3' end processing.
BIK 蛋白是线粒体凋亡的启动子,BIK 的表达受促凋亡信号诱导,包括 DNA 损伤。在这里,我们证明 3' 端加工和 BIK mRNA 的表达受核 PI4,5P(2)调节的多聚(A)聚合酶 Star-PAP 控制,后者下游受 DNA 损伤的影响。核 PKCδ 是细胞凋亡的关键介质,DNA 损伤刺激 PKCδ 与 Star-PAP 复合物结合,PKCδ 是 Star-PAP 依赖性 BIK 表达所必需的。PKCδ 结合产生 PI4,5P(2)的酶 PIPKIα,这对于 PKCδ 与 Star-PAP 复合物的相互作用至关重要,并且 PI4,5P(2)直接刺激 PKCδ 的活性。BIK 3' UTR 中的特征独特地定义了 Star-PAP 的特异性,并可能阻止 BIK mRNA 的典型 PAP 活性。这揭示了一个核磷酸肌醇信号连接体,其中 PIPKIα、PI4,5P(2)和 PKCδ 调节 Star-PAP 对 BIK 表达和凋亡诱导的控制。该途径不同于 Star-PAP 介导的氧化应激途径,表明对 mRNA 3' 端加工的信号特异性调节。