Casein kinase 1 regulates human hypoxia-inducible factor HIF-1
Casein kinase 1 regulates human hypoxia-inducible factor HIF-1
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DOI：
10.1242/jcs.068122
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发表时间：
2010-09-01
影响因子：
4
通讯作者：
Simos, George
中科院分区：
文献类型：
--
作者：
Kalousi, Alkmini;Mylonis, Ilias;Simos, George
低氧诱导因子-1(HIF-1)是一种转录激活因子，介导细胞对低氧的反应，是抗癌治疗的重要靶点，在低氧适应、胚胎发育和肿瘤进展中起着至关重要的作用。HIF-1是HIF-1α和HIF-1β(或ARNT)的异源二聚体，HIF-1α的表达受氧水平和各种氧非依赖机制的控制。在这项工作中，我们研究了HIF-1α的N末端异源二聚化(PAS)结构域的磷酸化，并确定Ser247是酪蛋白激酶1增量(CK1 Delta)体外修饰的主要位点。令人惊讶的是，该位点突变为丙氨酸，增强了HIF-1α的转录活性，这一结果是通过抑制或小干扰RNA(SiRNA)介导的低氧条件下CK1三角洲的沉默来实现的。反之，CK1 Delta的过表达或Ser247向天冬氨酸的拟磷突变抑制了HIF-1α的活性，而不影响其稳定性或核聚集。免疫沉淀和体外结合实验表明，CK1依赖的HIF-1α在Ser247位的磷酸化削弱了其与Arnt的结合，这一观点也被HIF-1α和Arnt PAS-B结构域之间的复合体的结构建模所支持。我们认为，CK1对HIF-1α的修饰是一种新的机制，通过调节HIF-1的两个亚基之间的相互作用来控制HIF-1在缺氧过程中的活性。
Hypoxia-inducible factor 1 (HIF-1), a transcriptional activator that mediates cellular response to hypoxia and a promising target of anticancer therapy, is essential for adaptation to low oxygen conditions, embryogenesis and tumor progression. HIF-1 is a heterodimer of HIF-1 alpha, expression of which is controlled by oxygen levels as well as by various oxygen-independent mechanisms, and HIF-1 beta (or ARNT), which is constitutively expressed. In this work, we investigate the phosphorylation of the N-terminal heterodimerization (PAS) domain of HIF-1 alpha and identify Ser247 as a major site of in vitro modification by casein kinase 1 delta (CK1 delta). Mutation of this site to alanine, surprisingly, enhanced the transcriptional activity of HIF-1 alpha, a result phenocopied by inhibition or small interfering RNA (siRNA)-mediated silencing of CK1 delta under hypoxic conditions. Conversely, overexpression of CK1 delta or phosphomimetic mutation of Ser247 to aspartate inhibited HIF-1 alpha activity without affecting its stability or nuclear accumulation. Immunoprecipitation and in vitro binding experiments suggest that CK1-dependent phosphorylation of HIF-1 alpha at Ser247 impairs its association with ARNT, a notion also supported by modeling the structure of the complex between HIF-1 alpha and ARNT PAS-B domains. We suggest that modification of HIF-1 alpha by CK1 represents a novel mechanism that controls the activity of HIF-1 during hypoxia by regulating the interaction between its two subunits.