SIGNAL-INDUCED DEGRADATION OF I-KAPPA-B-ALPHA REQUIRES SITE-SPECIFIC UBIQUITINATION
SIGNAL-INDUCED DEGRADATION OF I-KAPPA-B-ALPHA REQUIRES SITE-SPECIFIC UBIQUITINATION
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DOI：
10.1073/pnas.92.24.11259
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发表时间：
1995-11-21
影响因子：
11.1
通讯作者：
BALLARD, DW
中科院分区：
文献类型：
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作者：
SCHERER, DC;BROCKMAN, JA;BALLARD, DW
抑制蛋白I kappa B α控制转录因子NF-kappa B的核输入，I kappa B α的抑制活性通过信号诱导的蛋白水解从细胞质室调节。先前的研究表明，丝氨酸残基32和36的信号依赖性磷酸化将I κ B α靶向泛素-蛋白酶体途径。在这里，我们提供的证据表明赖氨酸残基21和22是信号诱导的κ B α泛素化的主要位点。Lys-21和Lys-22上保守的Lys- b> Arg替换在体内产生I kappa B α的显性阴性突变体。这些组成型抑制剂被适当磷酸化，但在多种诱导剂（包括病毒蛋白、细胞因子和通过t细胞受体模拟抗原刺激的药物）的作用下不能释放NF-kappa B。此外，这些Lys -> Arg突变阻止了体内I κ B α的信号依赖性降解和体外泛素偶联。我们得出结论，在Lys-21和/或Lys-22位点磷酸化的I κ B α泛素化是nf - κ B激活的必要步骤。
The inhibitor protein I kappa B alpha controls the nuclear import of the transcription factor NF-kappa B. The inhibitory activity of I kappa B alpha is regulated from the cytoplasmic compartment by signal-induced proteolysis. Previous studies have shown that signal-dependent phosphorylation of serine residues 32 and 36 targets I kappa B alpha to the ubiquitin-proteasome pathway. Here we provide evidence that lysine residues 21 and 22 serve as the primary sites for signal-induced ubiquitination ofI kappa B alpha. Conservative Lys --> Arg substitutions at both Lys-21 and Lys-22 produce dominant-negative mutants of I kappa B alpha in vivo. These constitutive inhibitors are appropriately phosphorylated but fail to release NF-kappa B in response to multiple inducers, including viral proteins, cytokines, and agents that mimic antigenic stimulation through the T-cell receptor. Moreover, these Lys --> Arg mutations prevent signal-dependent degradation of I kappa B alpha in vivo and ubiquitin conjugation in vitro. We conclude that site-specific ubiquitination of phosphorylated I kappa B alpha at Lys-21 and/or Lys-22 is an obligatory step in the activation of NF-kappa B.