Mizuguchi G, Vassilev A, Tsukiyama T, Nakatani Y, Wu C
Laboratory of Molecular Cell Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Biol Chem. 2001 May 4;276(18):14773-83. doi: 10.1074/jbc.M100125200. Epub 2001 Feb 5.
Drosophila nucleosome remodeling factor (NURF) is an ISWI-containing protein complex that facilitates nucleosome mobility and transcriptional activation in an ATP-dependent manner. Numerous studies have implicated histone acetylation in transcriptional activation. We investigated the relative contributions of these two chromatin modifications to transcription in vitro of a chromatinized adenovirus E4 minimal promoter that contains binding sites for the GAL4-VP16 activator. We found that NURF could remodel chromatin and stimulate transcription irrespective of the acetylation status of histones. In contrast, hyperacetylation of histones in the absence of NURF was unable to stimulate transcription, suggesting that NURF-dependent chromatin remodeling is an obligatory step in E4 promoter activation. When chromatin templates were first hyperacetylated and then incubated with NURF, significantly greater transcription stimulation was observed. The results suggest that changes in chromatin induced by acetylation of histones and the mobilization of nucleosomes by NURF combine synergistically to facilitate transcription. Experiments using single and multiple rounds of transcription indicate that these chromatin modifications stimulate transcription preinitiation as well as reinitiation.
果蝇核小体重塑因子（NURF）是一种含ISWI的蛋白复合物，它以ATP依赖的方式促进核小体移动和转录激活。大量研究表明组蛋白乙酰化与转录激活有关。我们研究了这两种染色质修饰对含有GAL4-VP16激活剂结合位点的染色质化腺病毒E4最小启动子体外转录的相对贡献。我们发现，无论组蛋白的乙酰化状态如何，NURF都能重塑染色质并刺激转录。相比之下，在没有NURF的情况下组蛋白的过度乙酰化无法刺激转录，这表明依赖NURF的染色质重塑是E4启动子激活的必要步骤。当染色质模板首先被过度乙酰化，然后与NURF一起孵育时，观察到显著更强的转录刺激。结果表明，组蛋白乙酰化诱导的染色质变化与NURF介导的核小体移动协同作用，促进转录。使用单轮和多轮转录的实验表明，这些染色质修饰刺激转录起始前以及重新起始。
