Laderoute Keith R, Calaoagan Joy M, Gustafson-Brown Cindy, Knapp A Merrill, Li Guo-Chun, Mendonca Holly L, Ryan Heather E, Wang Zhaohui, Johnson Randall S
Pharmaceutical Discovery Division, SRI International, Menlo Park, California 94025, USA.
Mol Cell Biol. 2002 Apr;22(8):2515-23. doi: 10.1128/MCB.22.8.2515-2523.2002.
Hypoxia (low-oxygen tension) is an important physiological stress that influences responses to a wide range of pathologies, including stroke, infarction, and tumorigenesis. Prolonged or chronic hypoxia stimulates expression of the stress-inducible transcription factor gene c-jun and transient activation of protein kinase and phosphatase activities that regulate c-Jun/AP-1 activity. Here we describe evidence obtained by using wild-type and HIF-1 alpha nullizygous mouse embryonic fibroblasts (mEFs) that the induction of c-jun mRNA expression and c-Jun phosphorylation by prolonged hypoxia are completely dependent on the presence of the oxygen-regulated transcription factor hypoxia-inducible factor 1 alpha (HIF-1 alpha). In contrast, transient hypoxia induced c-jun expression in both types of mEFs, showing that the early or rapid induction of this gene is independent of HIF-1 alpha. These findings indicate that the c-jun gene has a biphasic response to hypoxia consisting of inductions that depend on the degree or duration of exposure. To more completely define the relationship between prolonged hypoxia and c-Jun phosphorylation, we used mEFs from mice containing inactivating mutations of critical phosphorylation sites in the c-Jun N-terminal region (serines 63 and 73 or threonines 91 and 93). Exposure of these mEFs to prolonged hypoxia demonstrated an absolute requirement for N-terminal sites for HIF-1 alpha-dependent phosphorylation of c-Jun. Taken together, these findings suggest that c-Jun/AP-1 and HIF-1 cooperate to regulate gene expression in pathophysiological microenvironments.
缺氧（低氧张力）是一种重要的生理应激，会影响对多种病理状况的反应，包括中风、梗死和肿瘤发生。长期或慢性缺氧会刺激应激诱导转录因子基因c-jun的表达，并短暂激活调节c-Jun/AP-1活性的蛋白激酶和磷酸酶活性。在此，我们描述了利用野生型和HIF-1α基因敲除的小鼠胚胎成纤维细胞（mEFs）获得的证据，即长期缺氧诱导的c-jun mRNA表达和c-Jun磷酸化完全依赖于氧调节转录因子缺氧诱导因子1α（HIF-1α）的存在。相比之下，短暂缺氧在两种类型的mEFs中均诱导了c-jun表达，表明该基因的早期或快速诱导独立于HIF-1α。这些发现表明，c-jun基因对缺氧有双相反应，包括依赖于暴露程度或持续时间的诱导。为了更全面地定义长期缺氧与c-Jun磷酸化之间的关系，我们使用了来自在c-Jun N端区域关键磷酸化位点（丝氨酸63和73或苏氨酸91和93）含有失活突变的小鼠的mEFs。将这些mEFs暴露于长期缺氧环境中表明，c-Jun的HIF-1α依赖性磷酸化绝对需要N端位点。综上所述，这些发现表明c-Jun/AP-1和HIF-1在病理生理微环境中协同调节基因表达。
