The Role of Snz and Sno Proteins in the Yeast Saccharomyces cerevisiae

调节生长和分裂的能力被认为是活细胞最重要的特征之一。然而，在自然界中，细胞大部分时间处于静止状态或稳定期，在此期间，调节非生长、非分裂细胞的途径变得至关重要。由于细胞的大部分生命可能在静止状态下度过，因此调节进入、存活和退出这种状态的能力对于物种生存来说与分裂能力一样重要。虽然静止状态具有明显的意义，但人们对细胞进入或退出这种状态或长时间生存的机制知之甚少，经历了各种威胁生命的压力，包括饥饿。 长期的目标是了解分子事件，这是重要的过程中进入，生存期间，并退出稳定期，静止状态，在酵母酿酒酵母。在先前的研究中发现了两个在稳定期诱导的新基因SNZ 1（SNooZe）和SNO 1（SNZ近端开放阅读框架）。SNZ和SNO基因是高度保守的基因家族的成员，它们以转录差异对的形式存在。大多数酵母菌株含有三个SNZ/SNO基因对。Snz蛋白是迄今为止发现的最高度保守的蛋白，存在于所有三个系统发育域，即古细菌，细菌和真核生物。该项目的大部分内容都集中在SNZ 1上。除了在稳定期的诱导外，SNZ 1还可被特定的氨基酸、嘌呤和嘧啶饥饿诱导。snz 1突变体还对6-氮尿嘧啶（UTP和GTP生物合成途径的抑制剂）非常敏感，并且这种敏感性通过加入尿嘧啶而被抑制。这些结果表明，Snzl蛋白，可能还有Sno 1蛋白，是生产嘧啶核苷酸所必需的，可能是通过调节或参与酵母在可怕的饥饿期间所需的补救途径。

The ability to regulate growth and division is recognized as one of the most important characteristics of living cells. However, in nature cells spend most of their time in a quiescent state or stationary phase, during which pathways that regulate non-growing, non-dividing cells become critical. Because most of a cell's life may be spent in a quiescent state, the ability to regulate entry into, survival during, and exit from this state is as important for species survival as the ability to divide. Although the quiescent state is of obvious significance, little is known about the mechanisms that allow cells to enter or exit this state or to survive for long periods of time, experiencing a variety of life-threatening stresses, including starvation. The long-term objective of this is to understand the molecular events that are important for the process of entry into, survival during, and exit from stationary phase, the quiescent state, in the yeast Saccharomyces cerevisiae. In prior research two novel genes, SNZ1 (SNooZe) and SNO1 (SNZ-proximal Open reading frame) that are induced in stationary phase were identified. SNZ and SNO genes are members of highly conserved gene families that are found in divergently transcribed pairs. Most yeast strains contain three SNZ/SNO gene pairs. Snz proteins are the most highly conserved proteins yet identified that are present in all three phylogenetic domains, i.e. the archaea, bacteria, and eucarya. The majority of this project focuses on SNZ1. In addition to its induction in stationary phase, SNZ1 is induced by specific amino acid, purine, and pyrimidine starvation. snzl mutants are also exquisitely sensitive to 6 azauracil, an inhibitor of the UTP and GTP biosynthetic pathways, and this sensitivity is suppressed by addition of uracil. These results suggest that Snzl protein, and probably also Sno 1 protein, is required for production of pyrimidine nucleotides, possibly through regulation of or involvement in a salvage pathway required in yeast during times of dire starvation.