Profiling The Compendium Of Changes In Saccharomyces cerevisiae Due To Mutations That Alter Availability Of The Main Methyl Donor S-Adenosylmethionine

The SAM1 and SAM2 genes encode for S-AdenosylMethionine (AdoMet) synthetase enzymes, with AdoMet serving as the main cellular methyl donor. We have previously shown that independent deletion of these genes alters chromosome stability and AdoMet concentrations in opposite ways in Saccharomyces cerevisiae. To characterize other changes occurring in these mutants, we grew wildtype, sam1∆/sam1∆, and sam2∆/sam2∆ strains in 15 different Phenotypic Microarray plates with different components and measured growth variations. RNA-Sequencing was also carried out on these strains and differential gene expression determined for each mutant. We explored how the phenotypic growth differences are linked to the altered gene expression, and hypothesize mechanisms by which loss of the SAM genes and subsequent AdoMet level changes, impact pathways and processes. We present six stories, discussing changes in sensitivity or resistance to azoles, cisplatin, oxidative stress, arginine biosynthesis perturbations, DNA synthesis inhibitors, and tamoxifen, to demonstrate the power of this novel methodology to broadly profile changes due to gene mutations. The large number of conditions that result in altered growth, as well as the large number of differentially expressed genes with wide-ranging functionality, speaks to the broad array of impacts that altering methyl donor abundance can impart. Our findings demonstrate that some cellular changes are directly related to AdoMet-dependent methyltransferases and AdoMet availability, some are directly linked to the methyl cycle and its role in production of several important cellular components, and others reveal impacts of SAM gene mutations on previously unconnected pathways.SAM1与SAM2基因编码S-腺苷甲硫氨酸（S-AdenosylMethionine, AdoMet）合成酶，而AdoMet是细胞内主要的甲基供体。我们此前的研究证实，在酿酒酵母（Saccharomyces cerevisiae）中单独缺失这两个基因，会以相反方式改变染色体稳定性与AdoMet水平。为表征这些突变体中发生的其他变化，我们将野生型、sam1∆/sam1∆及sam2∆/sam2∆菌株接种至15种成分各异的表型微阵列（Phenotypic Microarray）平板中培养，并定量检测其生长差异。同时对上述菌株开展RNA测序（RNA-Sequencing）分析，确定各突变体的差异基因表达谱。我们解析了表型生长差异与基因表达改变之间的关联，并提出假说，阐释SAM基因缺失及后续AdoMet水平变化如何影响各类细胞通路与生物学过程。本研究呈现六项案例，分别讨论菌株对唑类药物、顺铂、氧化应激、精氨酸生物合成扰动、DNA合成抑制剂以及他莫昔芬的敏感性或抗性变化，以此展示该新型方法在全面解析基因突变所致表型改变方面的应用效能。大量可引发生长改变的实验条件，以及功能覆盖范围广泛的海量差异表达基因，均表明甲基供体丰度改变可产生极为广泛的细胞效应。本研究结果证实，部分细胞变化直接与AdoMet依赖型甲基转移酶及AdoMet可用性相关，部分直接关联甲基循环及其在多种关键细胞组分生成中的作用，其余发现则揭示了SAM基因突变对此前未被关联通路的调控影响。