Small ubiquitin-related modifier-1 modification mediates resolution of CREB-dependent responses to hypoxia
Small ubiquitin-related modifier-1 modification mediates resolution of CREB-dependent responses to hypoxia
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DOI：
10.1073/pnas.0337412100
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发表时间：
2003-02-04
影响因子：
11.1
通讯作者：
Taylor, CT
中科院分区：
文献类型：
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作者：
Comerford, KM;Leonard, MO;Taylor, CT
依赖于磷酸化的泛素化与转录调节蛋白酶体的降解相结合是最近被认可的一种控制一些炎症基因的机制。关于在解析过程中抑制这些途径中转录活动的反调节机制，人们知之甚少。在这里，我们研究了T84细胞中缺氧诱导的肿瘤坏死因子(TNF)α的瞬时性质，我们先前已经证明这一过程涉及cAMP反应元件结合蛋白(CREB)的磷酸化依赖的降解。初步研究表明，缺氧诱导的肿瘤坏死因子α是一种短暂的事件，其解决与出现一种更高分子量的CREB修饰形式有关。对来自低氧细胞的mRNA的基因阵列分析证实，小泛素相关修饰物(SUMO)-1mRNA的诱导依赖于时间。在长期低氧条件下，CREB在翻译后被SUMO-1修饰。此外，SUMO-1的过表达稳定了CREB在低氧条件下的表达，并增强了CREB依赖的报告基因的活性。赖氨酸残基K285和K304的定点突变在体内和体外都证明它们是相扑受体。K304的突变还导致CREB核定位的丧失，暗示该位点的SUMO-1修饰在CREB的亚细胞定位中起作用。因此，在长时间的低氧中，CREB通过与SUMO-1结合而被修饰。此外，我们假设，这种事件稳定并促进了CREB的核定位，从而补充了缺氧诱导的炎症过程的内源性分解阶段。
Phosphorylation-dependent ubiquitination combined with proteasomal degradation of transcriptional regulators is a recently appreciated mechanism for control of a number of inflammatory genes. Far less is known about the counterregulatory mechanisms that repress transcriptional activity in these pathways during resolution. Here, we investigated the transient nature of hypoxia-induced tumor necrosis factor (TNF)alpha in T84 cells, a process we have previously shown to involve phosphorylation-dependent degradation of the cAMP-response element-binding protein (CREB). Initial studies indicate hypoxia-induced TNFalpha to be a transient event, the resolution of which is associated with the appearance of a higher molecular weight modified form of CREB. Gene array analysis of mRNA derived from hypoxic cells identified a time-dependent induction of small ubiquitin-related modifier (SUMO)-1 mRNA. In prolonged hypoxia, CREB is posttranslationally modified by SUMO-1. Furthermore, SUMO-1 overexpression stabilizes CREB in hypoxia and enhances CREB-dependent reporter gene activity. Site-directed mutagenesis of lysine residues K285 and K304 identifies them as SUMO acceptors in vivo and in vitro. Mutation of K304 also results in loss of CREB nuclear localization, implying a role for SUMO-1 modification at this site in the subcellular localization of CREB. Thus, in prolonged hypoxia, CREB is modified by association with SUMO-1. Furthermore, we hypothesize that such an event stabilizes and promotes nuclear localization of CREB and thus complements an endogenous resolution phase for hypoxia-induced inflammatory processes.