Smad3 recruits the anaphase-promoting complex for ubiquitination and degradation of SnoN.
Smad3 recruits the anaphase-promoting complex for ubiquitination and degradation of SnoN.
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DOI：
10.1101/gad.912901
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发表时间：
2001-11
影响因子：
10.5
通讯作者：
S. L. Stroschein;S. Bonni;Jeffrey L. Wrana;K. Luo
中科院分区：
文献类型：
--
作者：
S. L. Stroschein;S. Bonni;Jeffrey L. Wrana;K. Luo
Smad蛋白介导转化生长因子- β (tgf - β)信号，调节细胞生长和分化。SnoN是tgf - β信号的重要负调控因子，在缺乏配体的情况下维持tgf - β靶基因的抑制状态。在tgf - β刺激下，Smad3和Smad2转运进入细胞核并诱导SnoN的快速降解，从而激活tgf - β靶基因。我们发现Smad2-或smad3诱导的SnoN降解需要泛素依赖性蛋白酶体，并可由后期促进复合体（APC）和UbcH5家族的泛素偶联酶介导。Smad3和Smad2在较小程度上与APC和SnoN相互作用，导致APC被SnoN招募，随后SnoN以破坏盒（D盒）依赖的方式泛素化。除了D盒外，SnoN的高效泛素化和降解还需要SnoN中的Smad3结合位点以及泛素附着所需的关键赖氨酸残基。Smad3结合位点或赖氨酸残基的突变都会导致SnoN的稳定，并增强tgf - β信号的拮抗作用。我们的研究阐明了SnoN降解的重要机制和途径，更重要的是揭示了APC在调节tgf - β信号传导中的新作用。
Smad proteins mediate transforming growth factor-beta (TGF-beta) signaling to regulate cell growth and differentiation. SnoN is an important negative regulator of TGF-beta signaling that functions to maintain the repressed state of TGF-beta target genes in the absence of ligand. On TGF-beta stimulation, Smad3 and Smad2 translocate into the nucleus and induce a rapid degradation of SnoN, allowing activation of TGF-beta target genes. We show that Smad2- or Smad3-induced degradation of SnoN requires the ubiquitin-dependent proteasome and can be mediated by the anaphase-promoting complex (APC) and the UbcH5 family of ubiquitin-conjugating enzymes. Smad3 and to a lesser extent, Smad2, interact with both the APC and SnoN, resulting in the recruitment of the APC to SnoN and subsequent ubiquitination of SnoN in a destruction box (D box)-dependent manner. In addition to the D box, efficient ubiquitination and degradation of SnoN also requires the Smad3 binding site in SnoN as well as key lysine residues necessary for ubiquitin attachment. Mutation of either the Smad3 binding site or lysine residues results in stabilization of SnoN and in enhanced antagonism of TGF-beta signaling. Our studies elucidate an important mechanism and pathway for the degradation of SnoN and more importantly, reveal a novel role of the APC in the regulation of TGF-beta signaling.