PHASE VARIATION IN SACCHAROMYCES CEREVISIAE

描述(逐字摘自申请人的摘要)：阶段变化是可遗传的、亚稳定的基因表达状态的通用术语。相变在细菌和真菌中已被描述，并与发病有关。菌落形态转换被认为是白色念珠菌的致病性状，因此在白念珠菌中得到了广泛的研究，但在这个系统中进行遗传分析一直是困难的。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，但在无毒的实验室菌株中没有。对单相识别基因座(PHI)的广泛遗传学研究表明，这很可能是由于tRNAochre抑制子在两种状态之间切换，PHI1-1和PHI1-2分别代表抑制状态和非抑制状态。研究人员描述的第二种相变形式是在甘露醇利用状态之间切换。通过互补来克隆PHI基因座是复杂的，因为这些状态是亚稳定的。取而代之的是，使用戴维斯实验室开发的技术，通过定位克隆策略来克隆这些基因座。一旦确定了PHI基因，对不同等位基因的测序可能会为转换机制提供线索。PHI基因将被引入非相变实验室菌株288C，以努力重建相变。

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.