Effect of MIG1 and SNF1 deletion on simultaneous utilization of glucose and xylose by Saccharomyces cerevisiae / 生物工程学报

Mig1 and Snf1 are two key regulatory factors involved in glucose repression of Saccharomyces cerevisiae. To enhance simultaneous utilization of glucose and xylose by engineered S. cerevisiae, single and double deletion strains of MIG1 and SNF1 were constructed. Combining shake flask fermentations and transcriptome analysis by RNA-Seq, the mechanism of Mig1 and Snf1 hierarchically regulating differentially expressed genes that might affect simultaneous utilization of glucose and xylose were elucidated. MIG1 deletion did not show any significant effect on co-utilization of mixed sugars. SNF1 deletion facilitated xylose consumption in mixed sugars as well as co-utilization of glucose and xylose, which might be due to that the SNF1 deletion resulted in the de-repression of some genes under nitrogen catabolite repression, thereby favorable to the utilization of nitrogen nutrient. Further deletion of MIG1 gene in the SNF1 deletion strain resulted in the de-repression of more genes under nitrogen catabolite repression and up-regulation of genes involved in carbon central metabolism. Compared with wild type strain, the MIG1 and SNF1 double deletion strain could co-utilize glucose and xylose, and accelerate ethanol accumulation, although this strain consumed glucose faster and xylose slower. Taken together, the MIG1 and SNF1 deletions resulted in up-regulation of genes under nitrogen catabolite repression, which could be beneficial to simultaneous utilization of glucose and xylose. Mig1 and Snf1 might be involved in the hierarchical regulatory network of genes under nitrogen catabolite repression. Dissection of this regulatory network could provide further insights to new targets for improving co-utilization of glucose and xylose.

Role of heme in mitochondrial biogensis: Transcriptional and post-transcriptional regulation of the expression of Iso-l-cytochrome C gene during glucose repression-derepression in cells of Saccharomyces cerevisiae.

Exogenous addition of hemin to glucose-repressed cells of Saccharomyces cerevisiae restores the level of Iso-1-cytochrome C messengers to that observed in derepressed cells. In vitro transcription in isolated nuclei has shown a 4-fold stimulation in the synthesis of Iso-1-cytochrome C messengers in repressed but hemin-treated and derepressed cells compared to the repressed cells. Studies on in vitro transport of RNA from isolated nuclei have revealed that there is a 50% drop in the transport of total RNA from nuclei isolated from repressed but hemin-treated and derepressed cells when compared with the nuclei from repressed cells. However, under these conditions, there is an enhanced transport of translatable RNA. Hybridization analysis of the transported RNA using Iso-1-cytochrome C gene-specific probe has shown that there is preferential transport of Iso-1-cytochrome C messengers in repressed but hemin treated and derepressed cells.

Mitochondrial RNA metabolism during mitochondriogenesis in yeast.

Mitochondrial transcription has been studied as a function of mitochondriogenesis in yeast cells. Two systems have been used: synchronously growing cells and cells subjected to glucose repression followed by derepression. Maximal RNA synthesis has been found in the S phase of the cell cycle and during the 'repressed' phase in asynchronous cells. Activities of RNA polymerase, poly A polymerase and incorporation of [32P]-into RNA in vitro are maximal at the same period. Gel analysis reveals the presence of some high molecular weight RNA species which are likely to be precursors. When chase experiments are carried out in the presence of excess glucose, the high molecular weight species remain unaffected, suggesting that RNA processing may be an important site of action of glucose repression.