权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Analysis of the amplification promoting sequence (EXP) in the ribosomal RNA gene

核糖体RNA基因中的扩增促进序列(EXP)的分析

基本信息

批准号：
17370065
负责人：
KOBAYASHI Takehiko
金额：
$ 9.91万
依托单位：
National Institute of Genetics (2006-2007)National Institute for Basic Biology (2005)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

项目摘要

The ribosomal RNA gene repeats (rDNA) is one of the most characteristic regions in eukaryotic chromosomes. The repeats consist of more than 100 tandem units occupying large part of the chromosome in most of organisms. Repeated genes families such as the ribosomal RNA genes (rDNA) are thought to be fragile sites for deletional recombination. However, as for the rDNA, cells have gene amplification system and recover copy number to the wild type level. We found a cis-essential sequence (EXP) for the amplification. In this research, I analyzed molecular mechanism of the EXP.First, we did the phylogenetic footprinting assay in the EXP using several kinds of yeasts and found a conserved region. Interestingly, the region was a bi-directional noncoding transcriptional promoter that is reported〜20 years ago. We tested the character of the promoter and found the transcription was essential for the amplification. Interestingly, when the rDNA copy number reduces, the transcription is activated and it removes cohesin from the region. As the result, unequal sister-chromatid recombination increases and amplification is induced. Then, when the copy number reaches around the wild type level, Sir2 protein represses the transcription and by the function of recovered cohesin the unequal sister-chromatid recombination is restricted. Like these, we found the copy number regulation system, that is, Sir2 regulates rDNA copy number through E-pro transcription by changing cohesin association.

核糖体RNA基因重复序列（rDNA）是真核生物染色体上最具特征的区域之一。在大多数生物体中，重复序列由100多个串联单位组成，占据染色体的大部分。重复基因家族如核糖体RNA基因（rDNA）被认为是缺失重组的脆弱位点。然而，对于rDNA，细胞具有基因扩增系统并将拷贝数恢复到野生型水平。我们发现了一个顺式必需序列（EXP）的扩增。在本研究中，我分析了EXP的分子机制。首先，我们用几种酵母对EXP进行了系统发育足迹分析，发现了一个保守的区域。有趣的是，该区域是一个双向非编码转录启动子，20年前就有报道。我们检测了启动子的特性，发现转录是扩增所必需的。有趣的是，当rDNA拷贝数减少时，转录被激活，并从该区域去除粘附素。结果，不等姐妹染色单体重组增加，并诱导扩增。然后，当拷贝数达到野生型水平时，Sir 2蛋白抑制转录，并且通过恢复的粘附素的功能限制不相等的姐妹染色单体重组。在此基础上，我们发现了rDNA拷贝数调控系统，即Sir 2通过改变cohesin的结合，通过E-pro转录调控rDNA拷贝数。