Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064, USA.
J Biol Chem. 2011 Nov 25;286(47):40556-65. doi: 10.1074/jbc.M111.289918. Epub 2011 Oct 6.
Analysis of in vivo chromatin remodeling at the PHO5 promoter of yeast led to the conclusion that remodeling removes nucleosomes from the promoter by disassembly rather than sliding away from the promoter. The catalytic activities required for nucleosome disassembly remain unknown. Transcriptional activation of the yeast PHO8 gene was found to depend on the chromatin-remodeling complex SWI/SNF, whereas activation of PHO5 was not. Here, we show that PHO8 gene circles formed in vivo lose nucleosomes upon PHO8 induction, indicative of nucleosome removal by disassembly. Our quantitative analysis of expression noise and chromatin-remodeling data indicates that the dynamics of continual nucleosome removal and reformation at the activated promoters of PHO5 and PHO8 are closely similar. In contrast to PHO5, however, activator-stimulated transcription of PHO8 appears to be limited mostly to the acceleration of promoter nucleosome disassembly with little or no acceleration of promoter transitions following nucleosome disassembly, accounting for the markedly lower expression level of PHO8.
对酵母 PHO5 启动子体内染色质重塑的分析得出结论，重塑通过解体而不是从启动子上滑离来去除启动子上的核小体。用于核小体解体的催化活性仍然未知。酵母 PHO8 基因的转录激活被发现依赖于染色质重塑复合物 SWI/SNF，而 PHO5 的激活则不是。在这里，我们表明，体内形成的 PHO8 基因环在 PHO8 诱导时失去核小体，表明通过解体去除核小体。我们对表达噪声和染色质重塑数据的定量分析表明，PHO5 和 PHO8 激活启动子处持续的核小体去除和再形成的动力学非常相似。然而，与 PHO5 不同的是，激活剂刺激 PHO8 的转录似乎主要局限于加速启动子核小体的解体，而核小体解体后启动子的转变几乎没有或没有加速，这解释了 PHO8 的表达水平明显较低。
