PDF(Pubmed)
Abstract：
A small non-histone protein of budding yeast, Nhp6 has been reported to specifically influence the transcription of a yeast gene, SNR6. The gene is essential, transcribed by the enzyme RNA polymerase III, and codes for the U6snRNA required for mRNA splicing. A translationally positioned nucleosome on the gene body enables the assembly factor TFIIIC binding by juxtaposing its otherwise widely separated binding sites, boxes A and B. We found histone depletion results in the loss of U6 snRNA production. Changing the rotational phase of the boxes and the linear distance between them with deletions in 5 bp steps displayed a helical periodicity in transcription, which gradually reduced with incremental deletions up to 40 bp but increased on further deletions enclosing the pseudoA boxes. Nhp6 influences the transcription in a dose-dependent manner, which is modulated by its previously reported co-operator, an upstream stretch of seven T residues centered between the TATA box and transcription start site. Nhp6 occupancy on the gene in vivo goes up at least 2-fold under the repression conditions. Nhp6 absence, T7 disruption, or shorter A-B box distance all cause the downstream initiation of transcription. The right +1 site is selected with the correct placement of TFIIIC before the transcription initiation factor TFIIIB. Thus, the T7 sequence and Nhp6 help the assembly and placement of the transcription complex at the right position. Apart from the chromatin remodelers, the relative rotational orientation of the promoter elements in nucleosomal DNA, and Nhp6 regulate the transcription of the SNR6 gene with precision.
摘要：
出芽酵母的一种小的非组蛋白，据报道，Nhp6特异性影响酵母基因的转录，SNR6。基因是必不可少的，由RNA聚合酶III转录，并编码mRNA剪接所需的U6snRNA。基因体上的翻译定位的核小体通过将其其他广泛分离的结合位点并置而使组装因子TFIIIC结合，框A和B。我们发现组蛋白耗尽导致U6snRNA产生的损失。改变盒子的旋转相位和它们之间的线性距离，以5bp的步长删除显示转录中的螺旋周期性，随着增量缺失逐渐减少，直至40bp，但随着围绕伪A盒的进一步缺失而增加。Nhp6以剂量依赖的方式影响转录，这是由其先前报道的合作者调制的，位于TATA框和转录起始位点之间的七个T残基的上游延伸。在抑制条件下，体内基因上的Nhp6占有率至少上升了2倍。Nhp6缺席，T7中断，或较短的A-B框距离均导致转录的下游起始。在转录起始因子TFIIIB之前正确放置TFIIIC来选择右+1位点。因此，T7序列和Nhp6有助于转录复合物的组装和放置在正确的位置。除了染色质重塑剂,核小体DNA中启动子元件的相对旋转方向，和Nhp6精确调控SNR6基因的转录。
