Institut de Recherche Interdisciplinaire, Université de Lille1 - Université de Lille2 - CNRS USR3078, Parc de la Haute Borne, 50 avenue de Halley, 59658 Villeneuve d'Ascq, France.
BMC Biochem. 2011 Feb 1;12:4. doi: 10.1186/1471-2091-12-4.
The human thymine-DNA glycosylase (TDG) plays a dual role in base excision repair of G:U/T mismatches and in transcription. Regulation of TDG activity by SUMO-1 conjugation was shown to act on both functions. Furthermore, TDG can interact with SUMO-1 in a non-covalent manner.
Using NMR spectroscopy we have determined distinct conformational changes in TDG upon either covalent sumoylation on lysine 330 or intermolecular SUMO-1 binding through a unique SUMO-binding motif (SBM) localized in the C-terminal region of TDG. The non-covalent SUMO-1 binding induces a conformational change of the TDG amino-terminal regulatory domain (RD). Such conformational dynamics do not exist with covalent SUMO-1 attachment and could potentially play a broader role in the regulation of TDG functions for instance during transcription. Both covalent and non-covalent processes activate TDG G:U repair similarly. Surprisingly, despite a dissociation of the SBM/SUMO-1 complex in presence of a DNA substrate, SUMO-1 preserves its ability to stimulate TDG activity indicating that the non-covalent interactions are not directly involved in the regulation of TDG activity. SUMO-1 instead acts, as demonstrated here, indirectly by competing with the regulatory domain of TDG for DNA binding.
SUMO-1 increases the enzymatic turnover of TDG by overcoming the product-inhibition of TDG on apurinic sites. The mechanism involves a competitive DNA binding activity of SUMO-1 towards the regulatory domain of TDG. This mechanism might be a general feature of SUMO-1 regulation of other DNA-bound factors such as transcription regulatory proteins.
人类胸腺嘧啶-DNA 糖基化酶（TDG）在碱基切除修复 G:U/T 错配和转录中发挥双重作用。SUMO-1 缀合对 TDG 活性的调节作用对这两种功能都有影响。此外，TDG 可以以非共价方式与 SUMO-1 相互作用。
我们使用 NMR 光谱学确定了 TDG 在赖氨酸 330 上发生共价 SUMO 化或通过位于 TDG C 端区域的独特 SUMO 结合基序（SBM）进行分子间 SUMO-1 结合时的不同构象变化。非共价 SUMO-1 结合诱导 TDG 氨基末端调节域（RD）的构象变化。这种构象动力学不存在于共价 SUMO-1 附着时，并且可能在调节 TDG 功能方面发挥更广泛的作用，例如在转录过程中。共价和非共价过程都能相似地激活 TDG G:U 修复。令人惊讶的是，尽管在 DNA 底物存在的情况下 SBM/SUMO-1 复合物解离，但 SUMO-1 仍然能够刺激 TDG 活性，表明非共价相互作用不直接参与 TDG 活性的调节。SUMO-1 在这里被证明通过与 TDG 的调节域竞争 DNA 结合来间接发挥作用。
SUMO-1 通过克服 TDG 对无嘌呤位点的产物抑制作用来增加 TDG 的酶周转率。该机制涉及 SUMO-1 对 TDG 调节域的竞争性 DNA 结合活性。这种机制可能是 SUMO-1 调节其他 DNA 结合因子（如转录调节蛋白）的一般特征。
