PHASE VARIATION IN SACCHAROMYCES CEREVISIAE

描述（逐字引用自申请人的摘要）：相位变异是可遗传的亚稳态基因表达状态的通用术语。相变化已在细菌和真菌中描述，并且与发病机制相关。菌落形态转换在白念珠菌中被广泛研究，因为它被认为是一种致病性状，但在这个系统中进行遗传分析一直很困难。PI发现，从人类患者中分离的酿酒酵母致病菌株发生了相变异，但在无毒实验室菌株中没有发生。一个相位同一性位点（PHI）的广泛的遗传表征表明，它最有可能是由于tRNA赭石抑制剂，在两种状态之间切换，PHI 1 -1和PHI 1 - 2，分别代表抑制和非抑制状态。研究者描述的第二种形式的相位变化是在甘露醇使用状态之间切换。通过互补克隆PHI基因座是复杂的，因为这些状态是亚稳态的。相反，这些基因座将使用戴维斯实验室开发的技术通过定位克隆策略进行克隆。一旦PHI基因被识别，不同等位基因的测序可能会提供开关机制的线索。PHI基因将被引入到非相变量实验室菌株288 c中，以重建相变量。

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.