Upstream activation factor (UAF) is a multifunctional transcription factor in Saccharomyces cerevisiae that plays dual roles in activating RNA polymerase I (Pol I) transcription and repression of Pol II. For Pol I, UAF binds to a specific upstream element in the ribosomal DNA (rDNA) promoter and interacts with two other Pol I initiation factors, the TATA-binding protein (TBP) and core factor (CF). We used an integrated combination of chemical cross-linking mass spectrometry (CXMS), molecular genetics, protein biochemistry, and structural modeling to understand the topological framework responsible for UAF complex formation. Here, we report the molecular topology of the UAF complex, describe new structural and functional domains that play roles in UAF complex integrity, assembly, and biological function, and provide roles for previously identified UAF domains that include the Rrn5 SANT and histone fold domains. We highlight the role of new domains in Uaf30 that include an N-terminal winged helix domain and a disordered tethering domain as well as a BORCS6-like domain found in Rrn9. Together, our results reveal a unique network of topological features that coalesce around a histone tetramer-like core to form the dual-function UAF complex.

中文翻译：

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RNA聚合酶I上游激活因子的分子拓扑。

上游激活因子（UAF）是啤酒酵母中的多功能转录因子，在激活RNA聚合酶I（Pol I）转录和抑制Pol II中起双重作用。对于Pol I，UAF与核糖体DNA（rDNA）启动子中的特定上游元件结合，并与其他两个Pol I起始因子TATA结合蛋白（TBP）和核心因子（CF）相互作用。我们使用化学交联质谱（CXMS），分子遗传学，蛋白质生物化学和结构建模的综合组合来了解负责UAF复合物形成的拓扑框架。在这里，我们报告了UAF复合体的分子拓扑，描述了在UAF复合体的完整性，组装和生物学功能中发挥作用的新结构和功能域，并为先前确定的包括Rrn5 SANT和组蛋白折叠域的UAF域提供角色。我们重点介绍了Uaf30中新域的作用，其中包括N末端有翼螺旋域和无序的束缚域，以及在Rrn9中发现的BORCS6样域。总之，我们的结果揭示了一个独特的拓扑特征网络，该网络围绕组蛋白四聚体样核心聚结在一起，形成了双重功能的UAF复合体。