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

热带假丝酵母（Candida tropicalis）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，热带假丝酵母通过增殖大量的过氧化物酶体来改变其细胞内结构。过氧化物酶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。伴随着过氧化物酶体增殖，过氧化物酶体酶的活性在正烷烃生长的细胞中被诱导。另一方面，它们在葡萄糖生长的细胞中以低速率合成或根本不合成。这种现象被称为葡萄糖抑制。异辛酸裂解酶（ICL）是乙醛酸循环的关键酶，位于过氧化物酶体中，受葡萄糖阻遏作用的控制。酿酒酵母启动子控制的葡萄糖阻遏机制被用来寻找顺式调控元件负责基因表达的去阻遏。各种反式作用因子， ...更多信息 在酿酒酵母中葡萄糖阻遏的遗传调控中，也被确定。UPR-ICL介导的热带假丝酵母在酿酒酵母中的转录仍然是葡萄糖抑制的，这一事实表明在两种酵母菌株中关于ICL基因的调控普遍存在类似的机制。分离了在乙酸盐培养基中不能解抑制UPR-ICL介导的基因表达的突变体，并分离了补充该突变的基因（FIL 1）。其中FILl被破坏的填充无效突变体不能在乙酸盐或乙醇上生长，并且酿酒酵母中由ICLl编码的异柠檬酸裂解酶的去阻遏也被缺陷。Fillp蛋白的氨基酸序列（230个氨基酸）与原核生物的核糖体循环因子（RRFs）相似。与原核RRF相比，Filip具有N-末端46个氨基酸的延伸，其显示能够作为线粒体靶向序列起作用。DELTAfil 1菌株的亚细胞分级显示DELTAfil 1菌株的线粒体部分的蛋白质组分不同于野生型菌株的那些，但类似于氯霉素处理的细胞或rho.细胞这些结果表明，Fillp是必需的线粒体中的蛋白质合成的S.结果表明，线粒体和细胞核之间存在一条通讯途径，当线粒体呼吸链缺乏时，该途径抑制编码乙醛酸循环和代谢途径关键酶的基因的表达。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