Analysis of the signal transduction of the formation of subcellular organelles, peroxisomes

热带假丝酵母是一种能利用正构烷烃作为唯一碳源和能源的无孢子二倍体酵母。在同化正构烷烃的过程中，热带梭菌通过增殖大量的过氧化物体改变了细胞内的结构。过氧化物体是一种多功能的单膜结合细胞器，存在于大多数真核细胞中。在正构烷烃生长的细胞中，伴随着过氧化物体的增殖，过氧化物酶的活性被诱导。另一方面，在葡萄糖培养的细胞中，它们的合成速度很低，甚至根本不合成。这种现象被称为葡萄糖抑制。异柠檬酸裂解酶(ICL)是乙醛酸循环的关键酶，定位于过氧化体中，受葡萄糖抑制作用的控制。利用葡萄糖抑制机制控制的酿酒酵母启动子寻找负责基因表达解除抑制的顺式调控元件。涉及…的各种反式作用因子在酿酒酵母葡萄糖抑制的遗传调控中也发现了更多的基因。在酿酒酵母中，UPR-ICL介导的热带葡萄球菌的转录仍然是葡萄糖抑制的，这一事实表明，在ICL基因的调控方面，两种酵母菌株普遍存在相似的机制。分离到一株在醋酸盐介质中不能抑制UPR-ICL介导的基因表达的突变体，并分离到与该突变互补的基因(Fill)。其中填充被破坏的填充缺失突变体不能在醋酸或乙醇上生长，在酿酒酵母中ICL1编码的异柠檬酸裂解酶的去阻遏也是缺陷的。Fillp的氨基酸序列(230个氨基酸)与原核生物的核糖体循环因子(RRF)具有相似性。与原核生物的RRFs相比，Fil IP的N端延伸有46个氨基酸，能够作为线粒体靶向序列发挥作用。亚细胞分离表明，DELTAfi 1菌株线粒体部分的蛋白质组分与野生型菌株不同，但与氯霉素处理的细胞或Rho相似。细胞。这些结果表明，Fillp是酿酒酵母线粒体蛋白质合成所必需的。结果表明，线粒体和细胞核之间存在一条通讯通路，当线粒体呼吸链存在缺陷时，该通路抑制乙醛酸循环和糖异生途径关键酶基因的表达。较少

Candida tropicalis is an asporogenic diploid yeast which is characterized by its ability to utilize n-alkanes as a sole carbon and energy source. In assimilating n-alkanes, C.tropicalis shows a change in its intracellular structure by proliferating a large number of peroxisomes. Peroxisomes are versatile, single-membrane-bound organelles occurring in most of eukaryotic cells. Concomitant with peroxisome proliferation, the activities of peroxisomal enzymes are induced in n-alkane-grown cells. On the other hand, they are synthesized at low rate or not at all in glucose-grown cells. This phenomenon is called as glucose repression. Isociterate lyase (ICL), a key enzyme of the glyoxylate cycle being localized in peroxisomes, is under the control of glucose repression. Promoters of Saccharomyces cerevisiae controlled by the glucose repression mechanism were used to search for cis-regulatory elements responsible for derepression of gene expression. Various trans-acting factors which are invol … More ved in the genetic regulation of the glucose repression in S.cerevisiae, were also identified. The fact that UPR-ICL-mediated transcription of C.tropicalis is still glucose-repressive in S.cerevisiae demonstrates that similar mechanisms are commonly existing in both of the yeast strains concerning the regulation of ICL gene. A mutant was isolated that failed to derepress the UPR-ICL-mediated gene expression in acetate medium, and the gene (FILl) that complemented this mutation was isolated. The fill null mutant in which FILl is disrupted could not grow on acetate or ethanol, and the derepression of the isocitrate lyase encoded by ICLl in S.cerevisiae was also defected. The amino acid sequence of Fillp (230 amino acids) showed similarity to ribosome recycling factors (RRFs) of prokaryotes. Compared to prokaryotic RRFs, Fil ip had an N-terminal 46 amino acid extension which was shown to be able to function as a mitochondrial targeting sequence. The subcellular fractionation of the DELTAfil 1 strain showed that protein constituents of the mitochondrial fraction of the DELTAfil 1 strain differed from those of the wild type strain, but resembled those of chloramphenicol-treated cells or rho。 cells. These results suggest that Fillp is necessary for protein synthesis in mitochondria of S.cerevisiae. The results indicate the presence of a communication pathway between mitochondria and the nucleus which represses expression of genes encoding the key enzymes of the glyoxylate cycle and gluconeogenic pathway when there is a deficiency in the mitochondrial respiratory chain. Less