SRY-box 2 (Sox2) is a transcription factor with critical roles in maintaining embryonic stem (ES) cell and adult stem cell functions and in tumorigenesis. However, how Sox2 exerts its transcriptional function remains unclear. Here, we used an in vitro protein-protein interaction assay to discover transcriptional regulators for ES cell core transcription factors (Oct4, Sox2, Klf4, and c-Myc) and identified members of the steroid receptor coactivators (SRCs) as Sox2-specific interacting proteins. The SRC family coactivators have broad roles in transcriptional regulation, but it is unknown whether they also serve as Sox2 coactivators. We demonstrated that these proteins facilitate Sox2 transcriptional activity and act synergistically with p300. Furthermore, we uncovered an acetylation-enhanced interaction between Sox2 and SRC-2/3, but not SRC-1, demonstrating it is Sox2 acetylation that promotes the interaction. We identified putative Sox2 acetylation sites required for acetylation-enhanced interaction between Sox2 and SRC-3 and demonstrated that acetylation on these sites contributes to Sox2 transcriptional activity and recruitment of SRC-3. We showed that activation domains 1 and 2 of SRC-3 both display a preferential binding to acetylated Sox2. Finally, functional analyses in mouse ES cells demonstrated that knockdown of SRC-2/3 but not SRC-1 in mouse ES cells significantly downregulates the transcriptional activities of various Sox2 target genes and impairs ES cell stemness. Taken together, we identify specific SRC family proteins as novel Sox2 coactivators and uncover the role of Sox2 acetylation in promoting coactivator recruitment and Sox2 transcriptional function.

中文翻译：

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转录因子 Sox2 和类固醇受体共激活因子之间的乙酰化增强相互作用促进了 Sox2 的转录活性和功能。

SRY-box 2 (Sox2) 是一种转录因子，在维持胚胎干 (ES) 细胞和成体干细胞功能以及肿瘤发生中具有关键作用。然而，Sox2 如何发挥其转录功能仍不清楚。在这里，我们使用体外蛋白质-蛋白质相互作用测定来发现 ES 细胞核心转录因子（Oct4、Sox2、Klf4 和 c-Myc）的转录调节因子，并将类固醇受体共激活因子 (SRC) 的成员鉴定为 Sox2 特异性相互作用蛋白质。SRC 家族共激活因子在转录调控中具有广泛的作用，但尚不清楚它们是否也可作为 Sox2 共激活因子。我们证明这些蛋白质促进 Sox2 转录活性并与 p300 协同作用。此外，我们发现了 Sox2 和 SRC-2/3 之间的乙酰化增强相互作用，但不是 SRC-1，证明是 Sox2 乙酰化促进了相互作用。我们确定了 Sox2 和 SRC-3 之间乙酰化增强相互作用所需的推定 Sox2 乙酰化位点，并证明这些位点上的乙酰化有助于 Sox2 转录活性和 SRC-3 的募集。我们发现 SRC-3 的激活域 1 和 2 都显示出与乙酰化 Sox2 的优先结合。最后，对小鼠 ES 细胞的功能分析表明，在小鼠 ES 细胞中敲除 SRC-2/3 而不是 SRC-1 会显着下调各种 Sox2 靶基因的转录活性并损害 ES 细胞干性。总之，我们将特定的 SRC 家族蛋白鉴定为新的 Sox2 共激活因子，并揭示了 Sox2 乙酰化在促进共激活因子募集和 Sox2 转录功能中的作用。