Wei Huijun, Wang Xianhui, Gan Boyi, Urvalek Alison M, Melkoumian Zara K, Guan Jun-Lin, Zhao Jihe
Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA.
J Biol Chem. 2006 Jun 16;281(24):16664-71. doi: 10.1074/jbc.M513135200. Epub 2006 Apr 13.
KLF8 (Krüppel-like factor 8) is a member of the Krüppel transcription factor family that binds CACCC elements in DNA and activates or represses their target genes in a context-dependent manner. Here we present sumoylation as a novel mechanism that regulates KLF8 post-translationally. We found that KLF8 can be covalently modified by small ubiqitin-like modifier (SUMO)-1, SUMO-2, and SUMO-3 in vivo. We showed that KLF8 interacted with the PIAS family of SUMO E3 ligases PIAS1, PIASy, and PIASxalpha but not with E2 SUMO-conjugating enzyme Ubc9. Furthermore, we demonstrated that the E2 and E3 ligases enhanced the sumoylation of KLF8. In addition, site-directed mutagenesis identified lysine 67 as the major sumoylation site on KLF8. Lysine 67 to arginine mutation strongly enhanced activity of KLF8 as a repressor or activator to its physiological target promoters and as an inducer of the G(1) cell cycle progression. Taken together, our results demonstrated that sumoylation of KLF8 negatively regulates its transcriptional activity and cellular functions.
KLF8（Krüppel样因子8）是Krüppel转录因子家族的成员，它能结合DNA中的CACCC元件，并以上下文依赖的方式激活或抑制其靶基因。在此，我们提出SUMO化是一种在翻译后调节KLF8的新机制。我们发现KLF8在体内可被小泛素样修饰物（SUMO）-1、SUMO-2和SUMO-3共价修饰。我们表明KLF8与SUMO E3连接酶PIAS1、PIASy和PIASxalpha的PIAS家族相互作用，但不与E2 SUMO结合酶Ubc9相互作用。此外，我们证明E2和E3连接酶增强了KLF8的SUMO化。另外，定点诱变确定赖氨酸67是KLF8上的主要SUMO化位点。赖氨酸67突变为精氨酸强烈增强了KLF8作为其生理靶启动子的阻遏物或激活物以及作为G(1)细胞周期进程诱导剂的活性。综上所述，我们的结果表明KLF8的SUMO化负向调节其转录活性和细胞功能。
