Project description:Interventions: Case series:None
Primary outcome(s): exon genes;transcriptional expression;proteome;protein phosphorylation group
Study Design: Sequential
Project description:In this study we have employed metabolomics approaches to understand the metabolic effects of producing enhanced green fluorescent protein (eGFP) as a recombinant protein in Escherichia coli cells. This metabolic burden analysis was performed against a number of recombinant expression systems and control strains and included: (i) standard transcriptional recombinant expression control system BL21(DE3) with the expression plasmid pET-eGFP, (ii) the recently developed dual transcriptional–translational recombinant expression control strain BL21(IL3), with pET-eGFP, (iii) BL21(DE3) with an empty expression plasmid pET, (iv) BL21(IL3) with an empty expression plasmid, and (v) BL21(DE3) without an expression plasmid; all strains were cultured under various induction conditions. The growth profiles of all strains together with the results gathered by the analysis of the Fourier transform infrared (FT-IR) spectroscopy data, identified IPTG-dependent induction as the dominant factor hampering cellular growth and metabolism, which was in general agreement with the findings of GC-MS analysis of cell extracts and media samples. In addition, the exposure of host cells to the synthetic inducer ligand, pyrimido[4,5-d] pyrimidine-2,4-diamine (PPDA), of the orthogonal riboswitch containing expression system (BL21(IL3)) did not display any detrimental effects, and its detected levels in all the samples were at similar levels, emphasising the inability of the cells to metabolise PPDA. The overall results obtained in this study suggested that although the BL21(DE3)-EGFP and BL21(IL3)-EGFP strains produced comparable levels of recombinant eGFP, the presence of the orthogonal riboswitch seemed to be moderating the metabolic burden of eGFP production in the cells enabling higher biomass yield, whilst providing a greater level of control over protein expression.
Project description:To study the induction of the genes encoding known and putative enzymes from the pectinolytic system of A. niger, the transcriptional profiles of 58 selected known or putative pectinolytic genes were monitored by microarray experiments. For this purpose, A. niger was cultivated on the complex substrates, sugar beet pectin and polygalacturonic acid as primary carbon sources. Galacturonic acid, rhamnose and xylose were used to assess the effects on gene expression caused by simple well-defined carbon sources, representing the most abundant sugar residues present in the backbone of pectin. Fructose, as a strong repressor of the expression of genes that are under carbon catabolite regulation, and sorbitol, as a non-inducing sugar-like alcohol, which does not affect the carbon catabolite regulation mechanisms were selected as control substrates. Mycelia of A. niger were pregrown for 18 h on 2% fructose, transferred to medium containing the different pectic and control substrates, and sampled at four time points during 24 h of incubation.
Project description:DNA microarrays were used to compare the E. coli gene expression response to soluble and insoluble recombinant protein production. The study objective was to characterize the dynamic transcriptional changes that occur as insoluble recombinant protein is produced
Project description:Aspergillus niger is a filamentous ascomycete fungus that is commonly found in most biotopes around the globe. In nature, A. niger degrades the plant biomass polysaccharides to monomeric sugars, transports them into the cells, and uses a variety of catabolic pathways to convert them into biochemical building blocks and energy. We show that when grown in liquid cultures, A. niger takes up plant-biomass derived monomeric sugars (and maltose) in a highly sequential manner, rather than simultaneously. Interestingly, this sequential uptake was not mediated by the fungal general carbon catabolite repressor protein CreA, which has been shown to mediate the use of preferential carbon sources over non-preferential carbon sources. Furthermore, transcriptome analysis strongly indicated that the preferential use of the monomeric sugars is arranged at the level of transport, but it is not reflected in transcriptional regulation of sugar catabolism. Therefore, the results indicate that the regulation of sugar transport and catabolism are separate physiological processes in A. niger.
Project description:Genome wide transcriptional profiling on liver mRNA retrieved from recombinant adenovirus A20 (rAd.A20) and rAd.bgalactosidase transduced livers, before and 24 hours after 78% extended liver resection. Overexpression of the NF-kB inhibitory protein A20 improves recovery of liver function and mass following extended liver resection and severe liver ischemia reperfusion injury in mice. In this project, we explored effects of A20 using transcriptional profiling on liver mRNA retrieved from recombinant adenovirus A20 (rAd.A20) and rAd.bgalactosidase transduced livers, before and 24 hours after 78% extended liver resection.
Project description:For over 30 years, serine hydroxamate has been used to chemically stimulate a stringent response in Escherichia coli and other bacteria. These studies have elucidated numerous characteristics of the classical stringent response beyond the simple cellular response to an amino acid shortage, including phospholipid synthesis and protease up-regulation. In this study, the effects of a serine hydroxamate addition on high cell density recombinant E. coli were examined and compared to the effects of recombinant protein production to determine overlaps, as recombinant protein production stress has often been attributed to amino acid shortages. Both the transcriptome and growth characteristics were evaluated and compared. The serine hydroxamate addition profoundly decreased the culture growth rate, whereas, recombinant protein production did not. Conversely, the transcriptome profile of the recombinant E. coli cultures were relatively unaffected by the serine hydroxamate addition, yet recombinant protein production dramatically changed the transcriptome profile. A subset of the classical stringent response genes were effected by the serine hydroxamate addition, whereas, recombinant protein production regulated numerous classical stringent response genes; however, not all. The genes that were regulated by the serine hydroxamate addition include numerous fatty acid synthesis genes, in agreement with altered phospholipids synthesis reports. These results indicate that recombinant protein production and the stringent response have many overlapping responses; however, are far from identical. It was hypothesized that recombinant protein production leads to a stringent response due to the high amino acid synthesis demands related to recombinant protein synthesis. A comparison of the transcriptomes during recombinant protein production and a chemical imposed stringent response would assist with determining what portion of the “metabolic burden” associated with recombinant protein production is due to amino acid shortages. In this study, the transcriptome profiles of recombinant E. coli were examined and compared for the three culture conditions: 1) Normal growth, no external stress; 2) L-serine hydroxamate addition (to mediate a stringent response); and 3) IPTG-induction to produce the recombinant protein chloramphenicol acetyltransferase (CAT). The transcriptome profiles from these three conditions were analyzed using Affymetrix Anti-sense E. coli GeneChip® microarrays.
Project description:Aspergillus niger produces a variety of lignocellulolytic enzymes (cellulases, hemicellulases, among others) and is regarded as cell factory for the production of heterologous proteins. Therefore, there is a growing interest in the study of its genes and the understanding of the cellular mechanisms in order to expand its applications. On the other hand, we have shown that enzyme production by A. niger is higher when grown forming biofilms than when grown conventionally in submerged systems. The objective of this study was to perform a global transcriptomic analysis and an expression analysis of both lignocellulases and biofilm regulatory genes as compared to A. niger in submerged culture. DNA microarray assays were performed to investigate the global gene expression which yielded information on the expression of more than 90% of A. niger genes. To further this comparison, the two culture systems were supplemented with different carbon sources (glucose, lactose, xylose and maltose) to establish a differential gene expression under different culture conditions. Also, to validate the differential expression qPCR was performed for quantitative comparison of the transcriptional level of genes in both culture systems.