Cell cycle regulation and chromosome organization in Caulobacter crescentus

染色体保存着维持生命的遗传信息。如果完全伸展，任何生物体的染色体DNA都将比包含它的细胞或细胞核长1000倍。因此，染色体必须大量压缩。此外，染色体DNA必须以一种能够并可能促进一系列重要细胞过程的方式进行包装和组织，包括DNA复制、染色体分离、转录、重组和修复。尽管染色体在细胞的生命中起着至关重要的中心作用，但它们的压实和组织机制仍未完全确定。在某种程度上，压缩是由DNA超卷曲驱动的，而DNA超卷曲是由一系列拓扑异构酶控制的。此外，大多数生物体编码一套DNA结合蛋白，直接形成、压缩和组织基因组DNA。这些蛋白质如何构建和组织DNA，以及它们的活动如何影响DNA复制、转录和染色体分离，人们仍然知之甚少，特别是在不编码组蛋白的细菌中。我们的目标是解决我们知识上的这一差距，使用遗传，生化和细胞生物学分析的组合来检查模式生物新月形茎杆菌，以及一组基因组规模的分析，包括ChIP-Seq， RNA-Seq和Hi-C。我们将重点阐明三个关键染色体组织成分在体内的功能和作用。具体来说，我们的目标是(i)剖析SMC（染色体结构维持）在建立Caulobacter染色体全局构型中的体内作用，（ii）阐明最近发现的核相关蛋白CnpA影响DNA拓扑结构、DNA复制和转录的机制，以及（iii）鉴定和表征组织末端并促进染色体分离的DNA结合蛋白。我们预计，研究Caulobacter学到的染色体组织机制和原理将广泛适用于其他细菌，并且考虑到染色体压实的普遍问题，也可能适用于真核生物。此外，由于紧致细菌染色体的一些核心蛋白质，如拓扑异构酶，是主要的抗生素靶点，我们的工作可能会为开发减缓或停止重要病原体增殖的新抗生素提供信息或指导。

Chromosomes harbor the genetic information thats support life. If fully stretched out, the chromosomal DNA of any organism would be ~1000 times longer than the cell or nucleus that contains it. Thus, chromosomes must be massively compacted. Additionally, chromosomal DNA must be packaged and organized in a manner that enables, and likely facilitates, a range of important cellular processes, including DNA replication, chromosome segregation, transcription, recombination, and repair. Despite the critical and central role of chromosomes in the life of a cell, the mechanisms responsible for their compaction and organization remain incompletely defined. Compaction is driven, in part, by DNA supercoiling, which is controlled by a series of topoisomerases. In addition, most organisms encode a suite of DNA-binding proteins that directly shape, compact, and organize genomic DNA. How these proteins structure and organize DNA, and how their activities impact DNA replication, transcription, and chromosome segregation remains poorly understood, particularly in bacteria, which do not encode histones. We aim to address this gap in our knowledge, examining the model organism Caulobacter crescentus using a combination of genetic, biochemical, and cell biological assays, along with a set of genome-scale assays, including ChIP-Seq, RNA-Seq, and Hi-C. We will focus on elucidating the in vivo functions and roles of three key chromosome organization components. Specifically, we aim to (i) dissect the in vivo role of SMC (structural maintenance of chromosomes) in establishing the global configuration of the Caulobacter chromosome, (ii) elucidate the mechanisms by which a recently identified nucleoid-assoicated protein called CnpA affects DNA topology, DNA replication, and transcription, and (iii) identify and characterize the DNA-binding proteins that organize the terminus and promote chromosome segregation. We anticipate that the mechanisms and principles of chromosome organization learned studying Caulobacter will be broadly relevant to other bacteria and, given the universal problem of chromosome compaction, likely to eukaryotes as well. Additionally, because some of the proteins central to compacting bacterial chromosomes, such as topoisomerases, are major antibiotic targets, our work may inform or guide the development of new antibiotics that slow or halt the proliferation of important pathogens.