Control Of Gene Expression During Development

发育过程中基因表达的控制

• 批准号: 6413259
• 负责人: JUDITH A KASSIS
• 金额: --
• 依托单位: EUNICE KENNEDY SHRIVER NATIONAL INSTITUTE OF CHILD HEALTH & HUMAN DEVELOPMENT
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6413259
• 关键词: DNA; Drosophilidae; binding proteins; binding sites; cell differentiation; gene expression; genetic regulation; growth /development; nucleic acid sequence; regulatory gene; transcription factor

During development and differentiation, genes become competent to be expressed or are stably silenced in an epigenetically heritable manner. This selective activation/repression of genes leads to the differentiation of tissue types. Our group is interested in the molecular mechanisms that lead to the heritable transmission of the silenced state. To address this problem, we are studying the mechanism of gene silencing by the Polycomb group genes (PcG) in Drosophila. The PcG genes encode a diverse group of proteins known to be important for silencing of homeotic and segmentation genes during development. Many PcG genes encode chromatin-associated proteins and it has been proposed that they silence transcription by forming protein complexes that inactivate chromatin. PcG proteins act through poorly defined cis-acting DNA sequences called Polycomb group Response Elements (PREs). PREs are thought to recruit PcG protein complexes to the DNA. We have completed a detailed study of one PRE from the segmentation gene engrailed. Our data suggest that the combination of sites for 5 DNA binding proteins are required for the function of this PRE. We identified one of the proteins that binds to this PRE as the product of the pleiohomeotic (pho) gene, a known PcG gene. pleiohomeotic encodes a Drosophila homolog of the mammalian zinc-finger transcription factor Yin Yang 1 (YY1). We call the Drosophila protein PHO. PHO and YY1 are 96% identical in sequence over 4 zinc fingers and share the same DNA binding specificity. Mutation of YY1/PHO binding sites within the engrailed PRE leads to a loss of PRE activity. We have also shown that YY1/PHO binding sites are required for the activity of another PRE, one from the homeotic gene Ultrabithorax. YY1/PHO binding sites have also been identified in many other PREs. These data suggest that PHO binding sites may be required for the function of many different PREs and we propose that PHO recruits or anchors PcG protein complexes to the DNA. If this were the case, then the phenotype of pho mutants should be severe derepression of homeotic and segmentation genes. However, the phenotype of pho mutants is only mild derepression. With the sequence of the Drosophila genome, a possible explanation to this apparent paradox was found. Another YY1 homolog exists in Drosophila. We are currently investigating whether this homolog functions in a manner similar to PHO during Drosophila development. To date, PcG proteins have been found in at least three distinct protein complexes. One question our laboratory is beginning to address is whether these different protein complexes act through different PREs. Although there are some sequence similarities between PREs, there are many differences, and one possibility is that these different elements recruit different PcG protein complexes using different DNA binding proteins. Our laboratory is therefore beginning a detailed analysis of another PRE to begin to understand the diversity of this important class of regulatory elements.

在开发和差异化过程中，基因能够以表观遗传遗传的方式表达或稳定地沉默。 这种基因的选择性激活/抑制导致组织类型的分化。我们的小组对导致沉默状态的传播传播的分子机制感兴趣。为了解决这一问题，我们正在研究果蝇中多康姆基基因（PCG）基因沉默的机理。 PCG基因编码了一组多样的蛋白质，对于在发育过程中的同源和分割基因沉默很重要。许多PCG基因编码与染色质相关的蛋白质，并已提出它们通过形成抗染色质的蛋白质复合物来使它们沉默。 PCG蛋白通过称为PolyComb组响应元件（PRES）的定义定义的顺式作用DNA序列起作用。人们认为PRES可以将PCG蛋白复合物募集到DNA。我们已经完成了一项详细的研究，该研究涉及分割基因的一个PRE。我们的数据表明，该PRE的功能需要5种DNA结合蛋白的位点组合。我们确定了与此PRE结合的一种蛋白质是已知的PCG基因（PHO）基因（PHO）基因的乘积。 Pleiohomeotic编码哺乳动物锌指转录因子Yin Yang 1（yy1）的果蝇同源物。我们称果蝇蛋白pho。 PHO和YY1在4个锌手指上的序列中相同96％，并且具有相同的DNA结合特异性。植入的YY1/PHO结合位点的突变预先导致活动丧失。我们还表明，YY1/PHO结合位点是另一个PRE的活性，一个来自同源基因超赤胆的活性。 YY1/PHO结合位点也已在许多其他PRES中鉴定出来。这些数据表明，许多不同PRES的功能可能需要PHO结合位点，我们建议将Pho募集或锚定在DNA上。如果是这种情况，那么Pho突变体的表型应严重消除同源和分割基因。但是，pho突变体的表型仅是轻度消除。通过果蝇基因组的序列，发现了这一明显悖论的可能解释。果蝇中存在另一个YY1同源物。 我们目前正在研究该同源物在果蝇发育过程中是否以类似于Pho的方式起作用。 迄今为止，在至少三个不同的蛋白质复合物中发现了PCG蛋白。我们的实验室开始解决的一个问题是，这些不同的蛋白质复合物是否通过不同的PRES起作用。尽管PRES之间存在一些序列相似性，但存在许多差异，其中一种可能性是这些不同的元素使用不同的DNA结合蛋白募集了不同的PCG蛋白复合物。因此，我们的实验室开始对另一个PRE进行详细分析，以开始了解这一重要的监管要素的多样性。