Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, Parma, Italy.
Mol Cell. 2010 May 28;38(4):614-20. doi: 10.1016/j.molcel.2010.04.016.
Small nucleolar RNAs (snoRNAs) play a key role in ribosomal RNA biogenesis, yet factors controlling their expression are unknown. We found that the majority of Saccharomyces snoRNA promoters display an aRCCCTaa sequence motif at the upstream border of a TATA-containing nucleosome-free region. Genome-wide ChIP-seq analysis showed that these motifs are bound by Tbf1, a telomere-binding protein known to recognize mammalian-like T(2)AG(3) repeats at subtelomeric regions. Tbf1 has over 100 additional promoter targets, including several other genes involved in ribosome biogenesis and the TBF1 gene itself. Tbf1 is required for full snoRNA expression, yet it does not influence nucleosome positioning at snoRNA promoters. In contrast, Tbf1 contributes to nucleosome exclusion at non-snoRNA promoters, where it selectively colocalizes with the Tbf1-interacting zinc-finger proteins Vid22 and Ygr071c. Our data show that, besides the ribosomal protein gene regulator Rap1, a second telomere-binding protein also functions as a transcriptional regulator linked to yeast ribosome biogenesis.
小核仁 RNA（snoRNAs）在核糖体 RNA 生物发生中发挥着关键作用，但控制其表达的因素尚不清楚。我们发现，大多数酿酒酵母 snoRNA 启动子在上游边界显示出一个 aRCCCTaa 序列基序，该基序位于包含 TATA 的无核小体区域。全基因组 ChIP-seq 分析表明，这些基序由 Tbf1 结合，Tbf1 是一种端粒结合蛋白，已知在端粒区识别哺乳动物样 T(2)AG(3)重复序列。Tbf1 有超过 100 个额外的启动子靶标，包括几个参与核糖体生物发生的其他基因和 TBF1 基因本身。Tbf1 是 snoRNA 充分表达所必需的，但它不影响 snoRNA 启动子处核小体的定位。相比之下，Tbf1 有助于非 snoRNA 启动子处核小体的排除，在那里它与 Tbf1 相互作用的锌指蛋白 Vid22 和 Ygr071c 选择性地共定位。我们的数据表明，除了核糖体蛋白基因调节因子 Rap1 之外，第二种端粒结合蛋白也作为与酵母核糖体生物发生相关的转录调节因子发挥作用。
