PHASE VARIATION IN SACCHAROMYCES CEREVISIAE

描述（摘自申请人摘要）：阶段变异是可遗传的、亚稳态的基因表达状态的总称。在细菌和真菌中已经描述了相变化，并与发病机制有关。由于菌落形态转换被认为是白色念珠菌的一种致病性状，因此对其进行了广泛的研究，但在该系统中进行遗传分析一直很困难。PI发现，从人类患者身上分离出来的酿酒酵母菌致病性菌株会发生相变，但在无毒的实验室菌株中不会发生相变。一相同一性位点（PHI）的广泛遗传特征表明，它很可能是由于tRNA赭石抑制子在PHI1-1和PHI1 -2两种状态之间切换，分别代表抑制状态和非抑制状态。研究者描述的第二种相变化形式是甘露醇利用状态之间的切换。由于状态是亚稳态的，通过互补克隆PHI基因座是复杂的。相反，这些基因座将通过使用戴维斯实验室开发的技术的位置克隆策略进行克隆。一旦PHI基因被确定，不同等位基因的测序可能为开关机制提供线索。将PHI基因引入非相位可变实验室菌株288c，以重建相位变化。

DESCRIPTION (Verbatim from the Applicant's Abstract): Phase variation is a general term for heritable, metastable gene expression states. Phase variation has been described in bacteria and fungi and is associated with pathogenesis. Colony morphology switching has been extensively studied in Candida albicans because it is considered to be a pathogenesis trait, but genetic analysis has been difficult in this system. The PI has discovered that phase variation occurs in pathogenic strains of Saccharomyces cerevisiae isolated from human patients, but not in avirulent laboratory strains. Extensive genetic characterization of one phase identity locus (PHI) has shown that it is most likely due to a tRNA ochre suppressor that switches between two states, PHI1-1 and PHI1 -2, representing suppressive and non suppressive states, respectively. The second form of phase variation described by the investigator is switching between mannitol utilization states. Cloning the PHI loci by complementation is complicated by the fact that the states are metastable. Instead, these loci will be cloned by a positional cloning strategy using technology developed in the Davis lab. Once the PHI genes are identified, sequencing of the different alleles might provide clues to the mechanism of switching. The PHI genes will be introduced to the non-phase variable laboratory strain, 288c, in efforts to reconstruct phase variation.