IDENTIFICATION OF FAB-7 BOUNDARY PROTEINS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 Fab-7边界的作用是确保果蝇双胸复合体中IAB-6和IAB-7顺式调节域从早期胚胎发育到成虫阶段的自主活性。虽然Fab-7只对单个后节段的正常发育是必需的，但它在所检测的所有组织和发育阶段都是活跃的。在这方面，Fab-7类似于果蝇和其他真核生物中通过无处不在的顺式元件和反式作用因子发挥作用的传统构成边界。Fab-7的边界跨越约1.2kb的DNA序列，包含3个染色质特异的核酸酶敏感位点。我们已经详细研究了这些最大的超敏感部位HS1中顺式作用序列的功能。虽然FAB-7的边界活动是本构的，但我们发现HS1被分成几个亚元素，其边界活动仅限于特定的发育阶段。其中一个亚元件位于HS1的近端，只在早期胚胎中活跃。第二个亚元件位于HS1的中间，在早期胚胎中不活跃；然而，它在胚胎发育中期变得活跃，然后一直活跃到成体阶段。HS1远端的第三个亚元件提供了从胚胎发育早期到中期的边界活动，但不是在胚胎发育后期。通过这个项目，我们确定了可能赋予这种早期特定边界活性的候选蛋白质，然后发现这些蛋白质形成了一个与靶序列结合的异质蛋白质复合体。我们还想确定在每个阶段中赋予其他阶段特定边界活动的反式作用因素。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The Fab-7 boundary functions to ensure the autonomous activity of the iab-6 and iab-7 cis-regulatory domains in the Drosophila Bithorax Complex from early embryogenesis through to the adult stage. Although Fab-7 is only required for the proper development of a single posterior parasegment, it is active in all tissues and stages of development that have been examined. In this respect Fab-7 resembles conventional constitutive boundaries in flies and other eukaryotes that act through ubiquitous cis-elements and trans-acting factors. The Fab-7 boundary spans a DNA sequence of ~1.2 kb and contains 3 chromatin specific nuclease hypersensitive sites. We have examined the functioning of cis-acting sequences in the largest of these hypersensitive sites, HS1, in detail. Though Fab-7 boundary activity is constitutive, we found that HS1 is divided into sub-elements whose boundary activity is restricted to only a specific stage in development. One sub-element, which is located on the proximal side of HS1, is active only in the early embryo. A second sub-element, which is located in the middle of HS1, is not active in early embryos; however, it becomes active mid-way through embryogenesis and then remains active through to the adult stage. A third sub-element on the distal side of HS1 confers boundary activity from early through mid-embryogenesis but not later. Through this project, we identified candidate proteins that are likely to confer this early-stage specific boundary activity, and then found that these proteins make a heterogeneous protein complex to bind the target sequence. We also would like to identify the trans-acting factors that confer other stage specific boundary activity in each.