Proteolytic turnover of the Gal4 transcription factor is not required for function in vivo
Proteolytic turnover of the Gal4 transcription factor is not required for function in vivo
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DOI：
10.1038/nature05067
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发表时间：
2006-08-31
期刊：
影响因子：
64.8
通讯作者：
Kodadek, Thomas
中科院分区：
文献类型：
--
作者：
Nalley, Kip;Johnston, Stephen Albert;Kodadek, Thomas
反式激活因子-启动子复合物是真核生物基因表达激活的重要中间体.最近对这些复合物的研究表明，由于分子伴侣对激活剂启动子复合物的快速和可逆破坏（2-6），或DNA结合激活剂的较慢的泛素-蛋白酶体途径介导的周转（7-9），一些复合物在活细胞中是相当动态的（1）。这些机制可以通过限制活性蛋白- DNA复合物的寿命来确保激活剂对信号级联的持续响应。此外，一些激活剂的效力受到蛋白酶体抑制的损害，从而提示激活剂从启动子的周期性清除对于高水平表达是必需的（8，10 -12）。在这里，我们描述了染色质免疫沉淀试验的一个变体，它允许直接观察天然Gal 4-启动子复合物在酵母中的动力学稳定性。在非诱导条件下，复合物是动态的，但在诱导时，Gal 4-启动子复合物“锁定”并表现出长半衰期。抑制蛋白酶体介导的蛋白水解对Gal 4介导的基因表达几乎没有影响。这些研究，结合早期的数据，表明不同的反式激活因子-启动子复合物在体内的寿命可以有很大的差异，蛋白酶体介导的周转不是反式激活因子功能的一般要求。
Transactivator - promoter complexes are essential intermediates in the activation of eukaryotic gene expression. Recent studies of these complexes have shown that some are quite dynamic in living cells(1) owing to rapid and reversible disruption of activator promoter complexes by molecular chaperones(2-6), or a slower, ubiquitin - proteasome-pathway-mediated turnover of DNA-bound activator(7-9). These mechanisms may act to ensure continued responsiveness of activators to signalling cascades by limiting the lifetime of the active protein - DNA complex. Furthermore, the potency of some activators is compromised by proteasome inhibition, leading to the suggestion that periodic clearance of activators from a promoter is essential for high-level expression(8,10-12). Here we describe a variant of the chromatin immunoprecipitation assay that has allowed direct observation of the kinetic stability of native Gal4-promoter complexes in yeast. Under non-inducing conditions, the complex is dynamic, but on induction the Gal4 - promoter complexes 'lock in' and exhibit long half-lives. Inhibition of proteasome-mediated proteolysis had little or no effect on Gal4-mediated gene expression. These studies, combined with earlier data, show that the lifetimes of different transactivator - promoter complexes in vivo can vary widely and that proteasome-mediated turnover is not a general requirement for transactivator function.