CHROMOSOME STURCTURE IN <I>E. COLI</I> AND <I>SCHIZOSACCHAROMYCES POMBE</I>

高阶染色质结构在基因调控、细胞类型决定和染色体遗传等许多细胞过程中起着至关重要的作用。我们发现，我们可以使用有毒物质樟脑来破坏染色质结构。樟脑在体内和体外都能脱密染色体。我们在大肠杆菌和裂糖菌中使用樟脑来分离基因，这些基因在过量生产时赋予细胞樟脑抗性。在大肠杆菌中，樟脑抗性鉴定出一个三基因系统。CrcA改变外膜的渗透性，给予部分樟脑抗性。CspE是一种冷休克样蛋白，CrcB是一种预测的疏水蛋白，它们负责染色体凝聚和完全樟脑抗性。我们已经证明，在体内和体外，这三个基因的过量生产导致更紧密凝聚的类核。如果我们过量生产CspE，我们可以证明部分樟脑抗性和类核凝结。CspE结合单链DNA、双链DNA和信使RNA。我们已经确定了CspE中仅能结合双链dna或单链核酸的突变。那些结合双链dna的突变体仍然能够进行染色体凝聚，而单链核酸结合突变体则不能。我们目前正在努力了解CspE是如何通过与dsDNA结合来凝聚染色体的。在S.pombe中，我们发现樟脑抗性可能是由于组蛋白去乙酰化酶Clr3和Clr6的过量产生。已知这两种蛋白质都影响高阶染色质结构，并且是沉默交配型位点的DNA所必需的。樟脑的选择也发现了一些新的基因，其中大约三分之一的基因也减少了交配型沉默和影响染色体稳定性。我们目前正在研究这些基因的性质和功能。总之，我们正在使用樟脑作为染色质结构的探针。这些研究将使我们能够确定高阶染色质结构是如何形成和维持的，从而允许完整和功能齐全的染色体被子细胞遗传。-细菌遗传学，染色体凝聚，大肠杆菌，分裂酵母遗传学，高阶染色质结构，裂糖菌，-既不是人类受试者，也不是人类组织

Higher order chromatin structure plays a vital role in many cellular processes including, gene regulation, cell type determination and chromosome inheritance. We have found that we can disrupt chromatin structure using the toxic agent, camphor. Camphor decondenses chromosomes both in vivo and in vitro. We have used camphor in both Escherichia coli and Schizosaccharomyces pombe to isolate genes, which when overproduced confer camphor resistance on cells. In E. coli, camphor resistance identified a three gene system. CrcA alters the permeability of the outer membrane to give partial camphor resistance. CspE, a cold-shock-like protein, and CrcB, a predicted hydrophobic protein, are responsible for chromosome condensation and complete camphor resistance. We have demonstrated that, both in vivo and in vitro, overproduction of the three genes results in more tightly condensed nucleoids. If we overproduce CspE alone, we can demonstrate partial camphor resistance and nucleoid condensation. CspE binds to single-stranded DNA, double-stranded DNA and messenger RNA. We have identified mutations in CspE that are capable of binding only dsDNA or only single stranded nucleic acids. Those that bind dsDNA are still capable of chromosome condensation, whereas single stranded nucleic acid binding mutants do not. We are currently working to understand how CspE condenses the chromosome through binding to dsDNA.In S.pombe, we have found that camphor resistance can result from overproduction of the histone deacetylases, Clr3 and Clr6. Both of these proteins are known to affect the higher order chromatin structure and to be required for silencing of the DNA of the mating type loci. The camphor selection has also identified several novel genes, with approximately one third of them also decreasing mating type silencing and affecting chromosome stability. We are currently investigating the nature and function of these genes.In summary, we are using camphor as a probe of chromatin structure. These studies will allow us to determine how higher-order chromatin structure is formed and maintained, thus allowing intact and fully functional chromosomes to be inherited by daughter cells. - Bacterial genetics, chromosome condensation, Escherichia coli, Fission Yeast Genetics, Higher Order Chromatin Sturcture, Schizosaccharomyces pombe, - Neither Human Subjects nor Human Tissues