MOLECULAR MECHANISMS OF TRANSCRIPTIONAL REPRESSION

描述：X染色体失活；表观遗传；位置 效应杂乱；基因座控制以及端粒沉默， 被抑制的交配型基因座和着丝粒都是转录的 染色质对真核生物基因组的调控特征 结构被认为是一种可能的控制因素。这个 假设的抑制性染色质结构域的确切性质尚未得到 对这些案件中的任何一个都已确定。探讨染色质在细胞周期调控中的作用 在DNA功能方面，研究人员将重点放在由 易驯化、简单的真核生物酿酒酵母中的交配型基因座。他 已经表明，抑制染色质结构是由 阿尔法细胞中阿尔法细胞特异性基因的α2抑制因子。的确有 这一有组织的染色质的存在的绝对一致性 在阿尔法细胞控制下完全抑制基因的结构 携带突变的组蛋白或突变的酵母菌株中的特异性启动子 在已知的抑制所必需的其他蛋白质(Ssn6p和Tuplp)中 这些基因。一个紧密堆积的二聚体核小体分离模体 43个碱基对跨越了整个被抑制的STE6基因。这个核小体 安排被认为是一种被压抑的组织范式 染色质结构域。拟议的研究将确定这一点是否 结构也出现在由alpha2控制的另一个基因上。 抑制子、Bari和其他需要SSn6p和Tuplp的基因 抑制，以及将Tuplp的抑制子定位于外源的模型系统 结合部位。SSn6p和Tuplp的域名表明他们的 参与蛋白质-蛋白质相互作用以及与蛋白质的相互作用 核基质结构。利用对微染色体的改进 在研究人员的实验室中率先建立了研究染色质的系统 组成和结构，他将分离出包含 STE6基因与SSN60和Tuplp基因的相互作用 被抑制的基因。对这些物质相互作用的生化研究 相互作用的蛋白质和染色体结构蛋白将定义 被抑制的染色质结构域的组成和结构。 最后，调查员将检查是否存在诸如 端粒、着丝粒和沉默的交配型基因座也有 密排二聚体的有序染色质结构 长链接器。为了解决这个问题，实验室将利用 酵母第三号染色体的全序列，并将绘制染色质图 约30kb的该染色体的结构。在专注于具体的 酵母中的基因组位点，这些研究与组织相关 在其他领域中被结构性抑制的遗传基因座，以及 酵母和更大的真核细胞中的条件性抑制基因。

DESCRIPTION: X-chromosome inactivation; epigenetic inheritance; position effect variegation; locus control as well as silencing at telomeres, repressed mating type loci, and centromeres are all transcriptionally regulated features of the eukaryotic genome for which chromatin structure has been suggested as a possible controlling element. The exact nature of the postulated repressive chromatin domain has not been determined for any of these cases. To explore the role of chromatin in DNA function, the investigator has focused on genes regulated by the mating type locus in a tractable, simple eukaryote, S. cerevisiae. He has shown that a repressive chromatin structure is organized by the alpha2 repressor on alpha-cell specific genes in alpha-cells. There is an absolute concordance of the presence of this organized chromatin structure with complete repression of genes under control of alpha-cell specific promoters in yeast strains bearing mutant histones or mutations in other proteins (Ssn6p and Tuplp) known to be necessary for repression of these genes. A motif of close packed dimeric nucleosomes separated by 43 bp linkers spans the entire repressed STE6 gene. This nucleosome arrangement is considered as a paradigm for organization of repressed chromatin domains. The proposed research will ascertain whether this structure also occurs for another gene controlled by the alpha2 repressor, BARI, other genes which require Ssn6p and Tuplp for repression, and model systems targeting a repressor of Tuplp to a foreign binding site. Ssn6p and Tuplp have domains which suggest their involvement in protein-protein interactions as well as interactions with nuclear matrix structures. Using improvements to the minichromosome system pioneered in the investigator's laboratory for study of chromatin composition and structure, he will isolate minichromosomes containing the STE6 gene and address directly the interaction of Ssn60 and Tuplp with the repressed gene. Biochemical studies of the interactions of these proteins with each other and chromosomal structural proteins will define the composition and structure of the repressed chromatin domain. Finally, the investigator will examine whether silenced domains such as telomeres, centromeres and the silent mating type loci also have the organized chromatin structure of close packed dimers interspersed by long linkers. To address this question, the lab will take advantage of the complete sequence of yeast chromosome III and will map chromatin structure of about 30 kb of this chromosome. While focusing on specific genomic loci in yeast, these studies are relevant to the organization of constitutively repressed genetic loci in other domains, as well as conditionally repressed genes in both yeast and larger eukaryotic cells.