Department of Plant Science, Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea.
Biochem Biophys Res Commun. 2010 Jul 23;398(2):242-6. doi: 10.1016/j.bbrc.2010.06.067. Epub 2010 Jun 19.
Ubiquitin is a small polypeptide and ubiquitination is the post-translational modification by ubiquitin protein, resulting in degradation of target proteins by the 26S proteasome complex. Here, we found that E3 ubiquitin ligase SINAT5, an Arabidopsis homologue of the Drosophila SINA RING-finger protein, interacts directly with LHY, a component of the circadian oscillator, and DET1, a negative regulator of light-regulated gene expression. We also found that SINAT5 has E3 ubiquitination activity for LHY but not for DET1. Interestingly, LHY ubiquitination by SINAT5 was inhibited by DET1. Late flowering of sinat5 mutants indicates that flowering time can be controlled by DET1 through regulation of LHY stability by SINAT5.
泛素是一种小的多肽，泛素化是由泛素蛋白进行的翻译后修饰，导致靶蛋白被 26S 蛋白酶体复合物降解。在这里，我们发现 E3 泛素连接酶 SINAT5，拟南芥果蝇 SINA 环指蛋白的同源物，直接与生物钟振荡器的组成部分 LHY 以及光调节基因表达的负调节剂 DET1 相互作用。我们还发现 SINAT5 对 LHY 具有 E3 泛素化活性，但对 DET1 没有。有趣的是，DET1 抑制 SINAT5 对 LHY 的泛素化。sinat5 突变体开花较晚表明开花时间可以通过 DET1 通过 SINAT5 调节 LHY 的稳定性来控制。
