Division of Translational Research, Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9185, USA.
J Biol Chem. 2009 Dec 11;284(50):34522-30. doi: 10.1074/jbc.M109.017277. Epub 2009 Oct 21.
It has been shown previously that sub-complexes of the 26 S proteasome can regulate gene expression via non-proteolytic mechanisms. One such mechanism is the disruption of activator.promoter complexes in an ATP-dependent fashion, which was discovered in the context of the yeast Gal4 system. This activity strongly inhibits Gal4-driven gene expression unless the activator is mono-ubiquitylated, which protects it from the ATPases. To address whether this paradigm is also applicable to medically important mammalian transcriptional activators we report here a study of the interaction of the proteasomal ATPases with p53. It is shown that p53 binds directly to the ATPases via its C-terminal tetramerization and regulatory domain and that p53.promoter complexes are indeed vulnerable to ATPase-dependent disruption by the ATPase complex in vitro. Knockdown of one of the ATPases, Rpt6, in living cells results in increased occupancy of the p21(waf1) promoter by p53 and increased expression of the gene, consistent with the idea that the proteasomal ATPases negatively regulate p53 function in a non-proteolytic fashion.
先前已经表明，26S 蛋白酶体的亚复合物可以通过非蛋白水解机制来调节基因表达。其中一种机制是通过 ATP 依赖性方式破坏激活剂-启动子复合物，这种机制是在酵母 Gal4 系统的背景下发现的。这种活性强烈抑制 Gal4 驱动的基因表达，除非激活剂被单泛素化，这可以保护它免受 ATP 酶的影响。为了确定这个范例是否也适用于医学上重要的哺乳动物转录激活剂，我们在这里报告了一项关于蛋白酶体 ATP 酶与 p53 相互作用的研究。结果表明，p53 通过其 C 末端四聚化和调节结构域直接与 ATP 酶结合，并且 p53-启动子复合物实际上容易受到体外 ATP 酶依赖性破坏。在活细胞中敲低其中一种 ATP 酶 Rpt6 会导致 p53 对 p21(waf1)启动子的占据增加，并增加基因的表达，这与蛋白酶体 ATP 酶以非蛋白水解方式负调控 p53 功能的观点一致。
