Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA.
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA.
Mol Cell. 2014 Mar 20;53(6):893-903. doi: 10.1016/j.molcel.2014.02.002. Epub 2014 Mar 6.
Ubiquitination of transcription activators has been reported to regulate transcription via both proteolytic and nonproteolytic routes, yet the function of the ubiquitin (Ub) signal in the nonproteolytic process is poorly understood. By use of the heterologous transcription activator LexA-VP16 in Saccharomyces cerevisiae, we show that monoubiquitin fusion of the activator prevents stable interactions between the activator and DNA, leading to transcription inhibition without activator degradation. We identify the AAA(+) ATPase Cdc48 and its cofactors as the Ub receptor responsible for extracting the monoubiquitinated activator from DNA. Our results suggest that deubiquitination of the activator is critical for transcription activation. These findings with LexA-VP16 extend in both yeast and mammalian cells to native transcription activators Met4 and R-Smads, respectively, that are known to be oligo-ubiquitinated. The results illustrate a role for Ub and Cdc48 in transcriptional regulation and gene expression that is independent of proteolysis.
泛素化的转录激活因子已被报道通过蛋白水解和非蛋白水解途径来调节转录，然而泛素（Ub）信号在非蛋白水解过程中的功能还知之甚少。通过在酿酒酵母中使用异源转录激活因子 LexA-VP16，我们表明激活剂的单泛素化融合阻止了激活剂与 DNA 之间的稳定相互作用，导致转录抑制而没有激活剂降解。我们鉴定出 AAA(+)ATP 酶 Cdc48 及其辅助因子是负责从 DNA 中提取单泛素化激活剂的 Ub 受体。我们的结果表明，激活剂的去泛素化对于转录激活至关重要。这些用 LexA-VP16 进行的研究结果分别在酵母和哺乳动物细胞中扩展到了天然转录激活因子 Met4 和 R-Smads，它们分别被证实是多泛素化的。这些结果表明 Ub 和 Cdc48 在转录调控和基因表达中具有独立于蛋白水解的作用。
