類泛素一號亞型離胺酸48的乙醯化調控蛋白質類泛素化

Abstract

類泛素化是一種重要的後轉譯修飾(PTM)，主要是用於調節許多細胞的功能。我們和其他人發現類泛素家族蛋白可以在多個離氨酸位置發生乙醯化，但是很少研究了解乙醯化是如何調控類泛素的結合與類泛素的共軛化。在這篇論文中，我們以類泛素一號亞型蛋白(SUMO-1)的乙醯化為主，探討SUMO-1的乙醯化是如何影響蛋白質的類泛素共軛化。首先，我們利用質譜分析證明細胞中的SUMO-1在第23、25、37、39、46和48號位置的離胺酸具有乙醯化。而且在這六個乙醯化的位置中，我們發現當細胞表現以模擬乙醯結構的谷安醯胺置換SUMO-1離胺酸48的蛋白後，SUMO-1的整體共軛化蛋白質明顯地受到改變。透過穩定同位素氨基酸細胞培養（SILAC）的定量方法和質譜分析，我們找到許多受到以模擬乙醯結構的谷安醯胺置換SUMO-1離胺酸48位置所改變的共軛蛋白質。接著我們利用體內和體外類泛素化的方法驗證這些被改變的共軛蛋白質，我們發現SUMO-1離胺酸48位置的乙醯化具有選擇性調節特定蛋白的類泛素共軛化功能:例如它可以使KAP1和PARP1的類泛素共軛化下降，但並不影響PML、RanGAP1和Daxx等蛋白的類泛素共軛化。這些研究結果顯示SUMO-1離胺酸48的乙醯化可以視為調控某些蛋白類泛素化的機轉。

SUMOylation is an important post-translational modification (PTM) in regulating many cellular functions. We and others found that SUMO paralogs can be acetylated at multiple lysine (K) residues. However, little is known about acetylation in controlling SUMO binding and conjugation. Here, we focused on SUMO-1 acetylation study as to how SUMO-1 acetylation affects SUMO binding and/or SUMO conjugation. We first demonstrated that SUMO-1 is acetylated at K23, 25, 37, 39, 46 or 48 in cells by Mass spectrometry (MS). Among these six acetylation sites, we found that expression of K48Q, an acetyl mimic, within SUMO-1 markedly affected global SUMO-1 conjugation. Through MS analysis and stable isotope amino acids cell culture (SILAC) quantitative approach, we identified SUMOylation of several substrates altered by SUMO-1 K48Q. By both in vivo and in vitro SUMOylation assays, we validated that SUMO-1 K48Ac selectively regulates certain substrates SUMOylation, including down- regulation of KAP1 and PARP1 SUMOylation, but not SUMOylation of PML, RanGAP1 and Daxx. These findings suggest that acetylation of SUMO-1 at K48 may function as a switch for fine-tuning certain protein SUMOylation.