Hsp90 Directly Modulates the Spatial Distribution of AF9/MLLT3 and Affects Target Gene Expression
Hsp90 Directly Modulates the Spatial Distribution of AF9/MLLT3 and Affects Target Gene Expression
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DOI：
10.1074/jbc.m110.101642
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发表时间：
2010-04-16
影响因子：
4.8
通讯作者：
Hemenway, Charles S.
中科院分区：
文献类型：
--
作者：
Lin, Jeffrey J.;Hemenway, Charles S.
AF9/MLLT3参与肾小管细胞上皮钠通道α编码基因ENaC α的调控。具体来说，AF9蛋白的增加导致ENaC α表达的减少，而AF9活性的变化似乎是肾脏醛固酮信号传导的重要组成部分。AF9存在于细胞核中，与组蛋白H3赖氨酸79甲基转移酶Dot1相互作用，而AF9也存在于细胞质中。本报告中的数据表明，热休克蛋白Hsp90作为Hsp90- hsp70 -p60/Hop伴侣复合物的一部分直接特异性地与AF9相互作用。新生物素抑制Hsp90功能的实验操作，而不是17-AAG，导致AF9从主要的核位置重新分布到细胞质位置。用siRNA敲低Hsp90可以模拟新生物霉素的作用。正如预期的那样，在Hsp90干扰下，AF9从细胞核向细胞质的转移导致ENaC α表达增加。这伴随着AF9在ENaC α启动子上的占用减少。我们的数据表明，Hsp90、Hsp70和p60/Hop与AF9的相互作用对于AF9的亚核定位和活性是必要的。AF9是越来越多被认为依赖于Hsp90复合体进行核靶向的核蛋白之一。
AF9/MLLT3 contributes to the regulation of the gene encoding the epithelial sodium channel alpha, ENaC alpha, in renal tubular cells. Specifically, increases in AF9 protein lead to a reduction in ENaC alpha expression and changes in AF9 activity appear to be an important component of aldosterone signaling in the kidney. Whereas AF9 is found in the nucleus where it interacts with the histone H3 lysine 79 methyltransferase, Dot1, AF9 is also present in the cytoplasm. Data presented in this report indicate that the heat shock protein Hsp90 directly and specifically interacts with AF9 as part of an Hsp90-Hsp70-p60/Hop chaperone complex. Experimental manipulation of Hsp90 function by the inhibitor novobiocin, but not 17-AAG, results in redistribution of AF9 from a primarily nuclear to cytoplasmic location. Knockdown of Hsp90 with siRNA mimics the effect elicited by novobiocin. As expected, a shift in AF9 from the nucleus to the cytoplasm in response to Hsp90 interference leads to increased ENaC alpha expression. This is accompanied by a decrease in AF9 occupancy at the ENaC alpha promoter. Our data suggest that the interaction of Hsp90, Hsp70, and p60/Hop with AF9 is necessary for the proper subnuclear localization and activity of AF9. AF9 is among a growing number of nuclear proteins recognized to rely on the Hsp90 complex for nuclear targeting.