Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, Israel.
The Shmunis School of Biomedicine & Cancer Research, Tel Aviv University, Tel Aviv, Israel.
PLoS Genet. 2022 Feb 14;18(2):e1010061. doi: 10.1371/journal.pgen.1010061. eCollection 2022 Feb.
The fission yeast TOR complex 2 (TORC2) is required for gene silencing at subtelomeric regions and for the induction of gene transcription in response to DNA replication stress. Thus, TORC2 affects transcription regulation both negatively and positively. Whether these two TORC2-dependent functions share a common molecular mechanism is currently unknown. Here, we show that Gad8 physically interacts with proteins that regulate transcription, including subunits of the Spt-Ada-Gcn5-acetyltransferase (SAGA) complex and the BET bromodomain protein Bdf2. We demonstrate that in the absence of TORC2, Gcn5, the histone acetyltransferase subunit of SAGA, accumulates at subtelomeric genes and at non-induced promoters of DNA replication genes. Remarkably, the loss of Gcn5 in TORC2 mutant cells restores gene silencing as well as transcriptional induction in response to DNA replication stress. Loss of Bdf2 alleviates excess of Gcn5 binding in TORC2 mutant cells and also rescues the aberrant regulation of transcription in these cells. Furthermore, the loss of either SAGA or Bdf2 suppresses the sensitivity of TORC2 mutant cells to a variety of stresses, including DNA replication, DNA damage, temperature and nutrient stresses. We suggest a role of TORC2 in transcriptional regulation that is critical for gene silencing and gene induction in response to stress and involves the binding of Gcn5 to the chromatin.
裂殖酵母 TOR 复合物 2（TORC2）对于端粒区域的基因沉默以及对 DNA 复制应激的基因转录诱导是必需的。因此，TORC2 负向和正向地影响转录调控。目前尚不清楚这两种依赖于 TORC2 的功能是否共享共同的分子机制。在这里，我们表明 Gad8 与调节转录的蛋白质（包括 Spt-Ada-Gcn5-乙酰转移酶（SAGA）复合物的亚基和 BET 溴结构域蛋白 Bdf2）物理相互作用。我们证明，在没有 TORC2 的情况下，Gcn5（SAGA 的组蛋白乙酰转移酶亚基）在端粒基因和未诱导的 DNA 复制基因启动子处积累。值得注意的是，在 TORC2 突变细胞中丧失 Gcn5 可恢复基因沉默以及对 DNA 复制应激的转录诱导。在 TORC2 突变细胞中丧失 Bdf2 可减轻 TORC2 突变细胞中 Gcn5 结合的过度，并挽救这些细胞中转录的异常调节。此外，缺失 SAGA 或 Bdf2 均可抑制 TORC2 突变细胞对各种应激（包括 DNA 复制、DNA 损伤、温度和营养应激）的敏感性。我们提出了 TORC2 在转录调控中的作用，该作用对于应激条件下的基因沉默和基因诱导至关重要，并且涉及 Gcn5 与染色质的结合。
