Acetylation of SUMO paralogs as a determinant of SUMO-mediated protein networks

通过磷酸化、乙酰化或泛素化对蛋白质进行的翻译后修饰（PTM）是控制细胞信号网络的中心机制。一般原理是通过特定的相互作用结构域选择性识别修饰的蛋白质。泛素相关的SUMO蛋白的修饰也调节特定的蛋白质-蛋白质相互作用，从而调节各种细胞信号传导过程。SUMO的连接通常标记蛋白质以被含有SUMO相互作用基序（SIM）的结合伴侣识别。突出的例子是靶向sumoylated RanGAP 1到RanBP 2或PML核体（NB）的SUMO/SIM依赖性组装。典型的西姆斯的特征在于一段疏水残基，其与SUMO表面上的疏水口袋相互作用。在SIM模块的一个子集中，酸性残基侧接疏水核心，并通过与改性剂上的碱性界面的静电相互作用增强与SUMO的结合。尽管在SUMO/SIM相互作用中有这些相对详细的分子见解，但尚不清楚这些相互作用的特异性和动力学如何调节。我们最近揭示了PTM在这一过程中的重要性。我们最初发现，在一个子集的SIM含有蛋白质的丝氨酸或苏氨酸残基，并置的疏水区域磷酸化。这些磷酸化SIM中磷酸化残基的额外负电荷增强了与SUMO基本界面的结合。最近，我们定义了位点特异性乙酰化的赖氨酸残基在这个基本的接口作为一种新的监管原则，在控制SUMO/SIM相互作用。我们可以证明SUMO 1在K37或SUMO 2在K33的乙酰化仍然允许与RanBP 2结合，但排除了与皮亚斯家族成员PML或Daxx的相互作用。因此，SUMO影响了PML NB的组装，特别是阻止了辅阻遏物Daxx向这些结构的SIM依赖性募集。重要的是，在生物化学实验中，我们可以进一步证明K33乙酰化的SUMO 2作为含溴结构域（BRD）的蛋白质p300的结合平台。在这个建议中，我们的目标是描绘乙酰化如何控制SUMO介导的蛋白质网络。我们的目标是确定乙酰SUMO修饰调控的特定底物，并寻求了解这如何影响选定的细胞途径，特别是基因表达的控制。 最后，我们希望解开SUMO的乙酰化是如何调节的。在资助期间，我们预计将达到以下里程碑：1。 破译SUMO旁系同源物上的特定乙酰基代码，该代码决定了 SUMO/SIM和乙酰-SUMO/BRD相互作用。 定义乙酰SUMO密码子的靶点并描述其对基因表达的影响. 识别控制SUMO旁系同源物乙酰化的调节成分和生理刺激。

The post-translational modification (PTM) of proteins through phosphorylation, acetylation or ubiquitylation is a central mechanism for the control of cellular signalling networks. A general principle is the selective recognition of the modified protein by a specific interaction domain. Modification by the ubiquitin-related SUMO protein also modulates specific protein-protein interactions thereby regulating various cellular signalling processes. Attachment of SUMO typically earmarks a protein for the recognition by a binding partner that contains a SUMO interaction motif (SIM). Prominent examples are the targeting of sumoylated RanGAP1 to RanBP2 or the SUMO/SIM-dependent assembly of PML nuclear bodies (NBs). Canonical SIMs are characterized by a stretch of hydrophobic residues, which interacts with a hydrophobic pocket on the surface of SUMO. In a subset of SIM modules acidic residues flank the hydrophobic core and enhance the binding to SUMO via electrostatic interactions with a basic interface on the modifier. Despite these relatively detailed molecular insights in SUMO/SIM interactions it is unclear how specificity and dynamics of these interactions are regulated. We recently unravelled the importance of PTMs for this process. We initially found that in a subset of SIM-containing proteins serine or threonine residues that juxtapose the hydrophobic region are phosphorylated. The additional negative charges of phosphorylated residues in these phosphoSIMs enhance the binding to the basic interface of SUMO. Very recently we defined site-specific acetylation of lysine residues within this basic interface as a novel regulatory principle in the control of SUMO/SIM interactions. We could show that acetylation of SUMO1 at K37 or SUMO2 at K33 still allows binding to RanBP2, but precludes the interaction with PIAS family members, PML or Daxx. Accordingly, SUMO affected the assembly of PML NBs and in particular prevented the SIM-dependent recruitment of the co-repressor Daxx to these structures. Importantly, in biochemical experiments we could further demonstrate that K33 acetylated SUMO2 serves as a binding platform for the Bromodomain (BRD) containing protein p300. In this proposal we aim to delineate how acetylation controls SUMO-mediated protein networks. We aim to identify specific substrates that are regulated by acetyl-SUMO modification and seek to get insight how this affects selected cellular pathways, in particular the control of gene expression. Finally, we want to unravel how the acetylation of SUMO is regulated.Within the funding period we anticipate to reach the following milestones:1. Decipher a specific acetyl-code on SUMO paralogs that determines the selectivity of SUMO/SIM and acetyl-SUMO/BRD interactions.2. Define targets of the acetyl-SUMO-code and delineate its impact on gene expression.3. Identify the regulatory components and physiological stimuli that control acetylation of SUMO paralogs.