Mechanisms of transcriptional regulation through chromatin in the commitment of the yeast cells

eukaryotic细胞中的基因表达与DNA包装的蛋白质的相互作用，是染色质的主要结构单元，包括一个组八聚氰胺和147对DNA的基础。由于核细胞组对转基因因子的访问受到了对其识别DNA位点的限制，核细胞组的定位被认为是转录调节的机制。在这项研究中，我们集中了核组定位在细胞特定基因BAR 1、早期Meiotic基因HOP 1和可诱导基因PHO 5和SNZ 1的调节中的作用。我们实施了一个新的策略，以测试定位核体在表达中的功能性特征，通过引入短、分化核体在一个精确的基因组区域中的干扰序列。增加多聚dA·多聚DT和多聚d（CG）·多聚d（GC）插入，它们可以形成B'构象和Z-DNA，相应地，导致的增加表达式。对核细胞波的基因组染色质结构的分析 ... More 促进区的位置被更长的多聚dA·多聚DT和多聚d（CG）·多聚d（CG）序列破坏。这些结果与一个想法一致，即核组定位在BAR 1和PHO 5的正确表达中发挥了重要作用。我们还展示了核组定位作用在确定HOP 1和SNZ 1基因的促进器无障碍性方面的重要作用。在增补中，我们展示了Isw 2和Itc 1是Isw 2染色质重塑复合体的基本组成部分，以定位BAR 1和HOP 1中的核体。最后，我们演示了在体内防止Hap 1激活子绑定的位置核组。这些结果在核细胞定位中有力地支持了该机制，以限制转录因子的访问。我们的结果也说明了DNA结构的内在属性使它们能够用于查询局部染色质功能的有用工具，如多样性细胞和组织，作为对体内基因表达的人工替代。Less（低）

Gene expression in eukaryotic cells involves the interactions of proteins with DNA packaged into nucleosomes, which are the primary structural units of chromatin, comprising a histone octamer and 147 base pairs of DNA. Since the nucleosome limits the access of trans-acting factors to their cognate DNA sites, nucleosome positioning has been proposed as a mechanism of transcriptional regulation. In this study, we focused roles of nucleosome positioning in regulation of a-cellspecific gene BAR1, an early meiotic gene HOP1, and inducible genes PHO5 and SNZ1. We implemented a new strategy to test the functional significance of the positioned nucleosomes in repression by introducing short, diverse nucleosome-disrupting sequences into a precise genomic region. Increased lengths of poly dA・poly dT and poly d(CG)・poly d(GC) inserts, which can form the B' conformation and Z-DNA, respectively, caused increased expression. Analyses of the genomic chromatin structure revealed that the nucleosome po … More sitions in the promoter regions are destabilized by longer poly dA・poly dT and poly d(CG)・poly d(CG) sequences. These results are consistent with the idea that nucleosome positioning plays an essential role in proper expression of BAR1 and PHO5. We also showed that nucleosome positioning plays important roles in determining promoter accessibility of HOP1 and SNZ1 genes. In addition, we showed that Isw2 and Itc1 are essential components of the Isw2 chromatin remodeling complex to position nucleosomes in BAR1 and HOP1. Finally, we demonstrated that a positioned nucleosome prevents Hap1 activator binding in vivo. These results strongly support the mechanism in which nucleosome positioning has a regulatory function to limit the access of transcription factors. Our results also illustrate that the intrinsic properties of DNA structure make them useful tools for inquiring into local chromatin function in diverse cells and organisms as well as for artificial alteration of gene expression in vivo. Less