Aki Toshihiko, Yoshida Ken-ichi, Mizukami Yoichi
Center for Gene Research, Yamaguchi University, 1-1-1 Minamikogushi, Ube, Yamaguchi, Japan.
Biochem Biophys Res Commun. 2003 Nov 7;311(1):162-7. doi: 10.1016/j.bbrc.2003.09.186.
The mechanism of small heat shock protein/alphaB-crystallin gene expression by proteasome inhibition was investigated. Expression of alphaB-crystallin was induced efficiently only by proteasome inhibition and not by heat shock while expression of HSP27 was induced efficiently by both proteasome inhibition and heat shock. The promoter of the alphaB-crystallin gene contains two conserved heat shock elements, one located between -397 and -374 and the other between -57 and -37, relative to the transcription start site. Electrophoretic mobility shift assay (EMSA) revealed that proteasome inhibition induces binding of heat shock factors to both heat shock elements in the alphaB-crystallin gene promoter. However, a transient transfection assay using deletion constructs of the alphaB-crystallin gene promoter showed that the region between -373 and -58 plays an important role in promoter activity. These results indicate the presence of differential response mechanisms of alphaB-crystallin gene expression to proteasome inhibition and heat shock, and that the activation of heat shock elements is not sufficient for the efficient induction of the alphaB-crystallin gene by proteasome inhibition.
研究了蛋白酶体抑制作用诱导小分子热休克蛋白/αB-晶状体蛋白基因表达的机制。仅蛋白酶体抑制作用能有效诱导αB-晶状体蛋白的表达，热休克则不能，而蛋白酶体抑制作用和热休克均能有效诱导HSP27的表达。相对于转录起始位点，αB-晶状体蛋白基因启动子包含两个保守的热休克元件，一个位于-397至-374之间，另一个位于-57至-37之间。电泳迁移率变动分析（EMSA）显示，蛋白酶体抑制作用可诱导热休克因子与αB-晶状体蛋白基因启动子中的两个热休克元件结合。然而，使用αB-晶状体蛋白基因启动子缺失构建体进行的瞬时转染分析表明，-373至-58之间的区域对启动子活性起重要作用。这些结果表明，αB-晶状体蛋白基因表达对蛋白酶体抑制作用和热休克存在不同的反应机制，且蛋白酶体抑制作用高效诱导αB-晶状体蛋白基因时，热休克元件的激活并不充分。
