Desmoucelles Christine, Pinson Benoit, Saint-Marc Christelle, Daignan-Fornier Bertrand
Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, 1 rue Camille Saint-Saens, 33077 Bordeaux Cedex, France.
J Biol Chem. 2002 Jul 26;277(30):27036-44. doi: 10.1074/jbc.M111433200. Epub 2002 May 16.
The immunosuppressive drug mycophenolic acid (MPA) is a potent and specific inhibitor of IMP dehydrogenase, the first committed step of GMP synthesis. A screen for yeast genes affecting MPA sensitivity, when overexpressed, allowed us to identify two genes, IMD2 and TPO1, encoding a homologue of IMP dehydrogenase and a vacuolar pump, respectively. In parallel, 4787 yeast strains, each carrying an identified knock-out mutation, were tested for growth in the presence of MPA, allowing identification of 100 new genes affecting MPA resistance when disrupted. Disturbance of several cellular processes, such as ergosterol biosynthesis, vacuole biogenesis, or glycosylation impaired the natural capacity of yeast to resist MPA, although most of the highly sensitive mutants affected the transcription machinery (19 mutants). Expression of TPO1 and/or IMD2 was strongly affected in 16 such transcription mutants suggesting that low expression of these genes could contribute to MPA sensitivity. Interestingly, the spt3, spt8, and spt20 mutants behaved differently than other Spt-Ada-Gcn5-acetyltransferase (SAGA) mutants. Indeed, in these three mutants, as in previously characterized transcription elongation mutants, IMD2 expression was only affected in the presence of MPA, thus suggesting a possible role for some SAGA subunits in transcription elongation.
免疫抑制药物霉酚酸（MPA）是肌苷单磷酸脱氢酶（IMP dehydrogenase）的强效特异性抑制剂，IMP脱氢酶是鸟苷单磷酸（GMP）合成的首个关键步骤。通过筛选过表达时影响MPA敏感性的酵母基因，我们鉴定出了两个基因，即IMD2和TPO1，它们分别编码IMP脱氢酶的一个同源物和一种液泡泵。同时，对4787个携带已鉴定敲除突变的酵母菌株进行了在MPA存在下的生长测试，从而鉴定出100个新的在被破坏时影响MPA抗性的基因。尽管大多数高度敏感的突变体影响转录机制（19个突变体），但干扰一些细胞过程，如麦角固醇生物合成、液泡生物发生或糖基化，会损害酵母抵抗MPA的天然能力。在16个这样的转录突变体中，TPO1和/或IMD2的表达受到强烈影响，这表明这些基因的低表达可能导致MPA敏感性。有趣的是，spt3、spt8和spt20突变体的行为与其他Spt - Ada - Gcn5 - 乙酰转移酶（SAGA）突变体不同。实际上，在这三个突变体中，如同在先前表征的转录延伸突变体中一样，IMD2的表达仅在MPA存在时受到影响，因此表明一些SAGA亚基在转录延伸中可能发挥作用。
