Zhao Yanmei, Lu Jun, Sun Hui, Chen Xia, Huang Baiqu
The Institute of Genetics and Cytology, Northeast Normal University, Changchun 130024, PR China.
Mol Cell Biochem. 2007 Dec;306(1-2):1-8. doi: 10.1007/s11010-007-9547-x. Epub 2007 Jul 10.
The promoter of the Drosophila hsp26 gene contains two DNase I-hypersensitive (DH) sites and a positioned nucleosome, and this open chromatin structure is required for heat-inducible expression. Histone acetylation modification participates in transcriptional regulation of genes by affecting the status of chromatin remodeling. In this study, we investigated the roles of histone acetylation modification on hsp26 expression in Drosophila. We showed that the histone deacetylase inhibitor (HDI) treatments of Drosophila larvae induced the histone H3 hyperacetylation at the promoter DH sites, which facilitated the binding of heat shock factor (HSF) to heat shock element (HSE). This resulted in a promoted transcription of hsp26 gene following the heat shock, and further increased the inducible expression of hsp26 gene. On the contrary, the HDI-induced histone H3 hyperacetylation in the middle nucleosome decreased the basal expression of hsp26 gene under the normal growth conditions. In addition, by following up the heat-shock time course, we showed that the histone acetylation level at the DH sites exhibited a drop-raise-drop change, while that at the positioned nucleosome underwent a raise-drop-raise-drop switchover. These results demonstrated the distinct roles played by histone acetylation modification in hsp26 gene basal and inducible expression regulation in D. melanogaster.
果蝇hsp26基因的启动子包含两个脱氧核糖核酸酶I超敏（DH）位点和一个定位核小体，这种开放染色质结构是热诱导表达所必需的。组蛋白乙酰化修饰通过影响染色质重塑状态参与基因的转录调控。在本研究中，我们调查了组蛋白乙酰化修饰对果蝇中hsp26表达的作用。我们发现，用组蛋白去乙酰化酶抑制剂（HDI）处理果蝇幼虫会诱导启动子DH位点处的组蛋白H3高度乙酰化，这促进了热休克因子（HSF）与热休克元件（HSE）的结合。这导致热休克后hsp26基因的转录得到促进，并进一步增加了hsp26基因的诱导表达。相反，HDI诱导的中间核小体中的组蛋白H3高度乙酰化降低了正常生长条件下hsp26基因的基础表达。此外，通过跟踪热休克时间进程，我们发现DH位点处的组蛋白乙酰化水平呈现下降-上升-下降的变化，而定位核小体处的组蛋白乙酰化水平则经历上升-下降-上升-下降的转换。这些结果证明了组蛋白乙酰化修饰在黑腹果蝇hsp26基因基础表达和诱导表达调控中所起的不同作用。
