MOLECULAR MECHANISMS OF TRANSCRIPTIONAL REPRESSION

描述：X染色体失活;表观遗传;位置 影响杂色;基因座控制以及端粒沉默， 抑制交配型基因座和着丝粒都是转录 真核基因组的调控特征， 结构被建议作为可能的控制元件。 的 假定的抑制性染色质结构域的确切性质尚未被 确定这些案件中的任何一个。 探讨染色质在 DNA功能，研究人员集中在基因调控的 交配型基因座在一个易处理的，简单的真核生物，S。 啤酒。 他 已经表明，抑制性染色质结构是由 在α细胞中α细胞特异性基因上的α 2阻遏物。 有 这种有组织的染色质的存在绝对一致 在α-细胞控制下基因完全阻遏结构 携带突变组蛋白或突变的酵母菌株中的特异性启动子 在其他蛋白质（Ssn 6p和Tuplp）已知是必要的抑制 这些基因。 分离的紧密堆积的二聚体核小体基序 通过43 bp的接头跨越整个阻遏的STE 6基因。 这个核小体 安排被认为是一种范式组织的压抑 染色质结构域。 这项研究将确定， 另一个由α 2控制的基因也发生了这种结构。 阻遏物，巴里，其他需要Ssn 6p和Tuplp的基因， 阻遏物，以及将Tuplp阻遏物靶向外源基因的模型系统。 结合位点 Ssn 6p和Tuplp的结构域表明， 参与蛋白质-蛋白质相互作用以及与 核基质结构。 利用对微型染色体的改进 在研究者实验室中开创的染色质研究系统 组成和结构，他将分离出含有 STE 6基因，并直接解决Ssn 60和Tuplp与 被压抑的基因 对这些物质之间相互作用的生物化学研究 蛋白质和染色体结构蛋白将定义 抑制染色质结构域的组成和结构。 最后，调查人员将检查是否沉默域，如 端粒，着丝粒和沉默交配型基因座也有 紧密排列的二聚体的有组织的染色质结构散布着 长链接器。 为了解决这个问题，实验室将利用 酵母染色体III的完整序列，并将绘制染色质 该染色体的约30 kb结构。 同时注重具体的 酵母的基因组位点，这些研究与组织有关， 在其他领域的组成性抑制基因位点，以及 酵母和较大的真核细胞中的条件性阻遏基因。

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.