TBP O-GlcNAcylation at T114 regulates formation of the B-TFIID complex and is critical for metabolic gene regulation.

In eukaryotes, gene expression is performed by three RNA polymerases that are targeted to promoters by molecular complexes. A unique common factor, the TATA-box binding protein (TBP), is thought to serve as a platform to assemble pre-initiation complexes competent for transcription. Herein, we describe a novel molecular mechanism of nutrient regulation of gene transcription by dynamic O-GlcNAcylation of TBP. We show that O-GlcNAcylation at T114 of TBP blocks its interaction with BTAF1, hence the formation of the B-TFIID complex, and its dynamic cycling on and off of DNA. Transcriptomic and metabolomic analyses of TBPT114A CRISPR/Cas9 edited cells showed that loss of O-GlcNAcylation at T114 increases TBP binding to BTAF1 and directly impacts expression of 408 genes. Lack of O-GlcNAcylation at T114 is associated with a striking reprograming of cellular metabolism induced by a profound modification of the transcriptome, leading to gross alterations in lipid storage.

在真核生物中，基因表达由三类RNA聚合酶（RNA polymerases）完成，这些聚合酶通过分子复合物靶向结合至启动子（promoter）。目前认为，一类独特的通用因子——塔塔框结合蛋白（TATA-box binding protein，TBP）可作为组装具备转录活性的预起始复合物的平台。本文报道了一种通过TBP的动态O-连接N-乙酰葡糖胺糖基化（O-GlcNAcylation）实现营养调控基因转录的全新分子机制。本研究发现，TBP第114位苏氨酸位点的O-连接N-乙酰葡糖胺糖基化会阻断其与BTAF1的相互作用，进而阻碍B-TFIID复合物的形成，并影响TBP在DNA上的动态循环结合与解离。对经CRISPR/Cas9编辑的TBPT114A细胞开展转录组学与代谢组学分析后发现，T114位点O-连接N-乙酰葡糖胺糖基化的缺失会增强TBP与BTAF1的结合，并直接影响408个基因的表达水平。T114位点O-连接N-乙酰葡糖胺糖基化的缺失，会引发因转录组显著改变所导致的细胞代谢重编程，最终造成脂质储存的严重异常。