Cell cycle regulation and chromosome organization in Caulobacter crescentus

染色体包含着支持生命的遗传信息。任何生物体的染色体DNA如果完全伸展开来，其长度将是细胞或细胞核的1000倍，因此，染色体必须被大量压缩。此外，染色体DNA必须以能够并且可能促进一系列重要细胞过程的方式包装和组织，包括DNA复制、染色体分离、转录、重组和修复。尽管染色体在细胞生命中起着关键和核心的作用，但负责其压实和组织的机制仍然没有完全确定。压缩部分是由DNA超螺旋驱动的，DNA超螺旋由一系列拓扑异构酶控制。此外，大多数生物体编码一套DNA结合蛋白，直接塑造，压缩和组织基因组DNA。这些蛋白质如何结构和组织DNA，以及它们的活性如何影响DNA复制，转录和染色体分离仍然知之甚少，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中的这一差距，使用遗传学，生物化学和细胞生物学测定的组合检查模式生物新月柄杆菌，沿着一组基因组规模的测定，包括ChIP-Seq，RNA-Seq和Hi-C。我们将着重阐明三个关键的染色体组织成分在体内的功能和作用。具体而言，我们的目标是（i）解剖SMC在体内的作用，（染色体的结构维持）在建立柄杆菌染色体的全局构型中的作用，（ii）阐明最近鉴定的称为CnpA的核相关蛋白影响DNA拓扑结构、DNA复制和转录的机制，和（iii）鉴定和表征组织末端和促进染色体分离的DNA结合蛋白。我们预计，研究柄杆菌学到的染色体组织的机制和原则将广泛适用于其他细菌，考虑到染色体致密化的普遍问题，也可能适用于真核生物。此外，由于一些对压缩细菌染色体至关重要的蛋白质，如拓扑异构酶，是主要的抗生素靶点，我们的工作可能会通知或指导新抗生素的开发，以减缓或阻止重要病原体的增殖。

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.