Heterologous Gene Expression in an Escherichia coli Population Under Starvation Stress Conditions (original) (raw)
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Expression of horizontally transferred gene clusters: activation by promoter-generating mutations
Research in Microbiology, 2001
The occurrence of promoter-generating mutations allowing the transcription of heterologous genes has been studied in a system based on the plasmid-mediated conjugal transfer of histidine biosynthetic genes from a donor bacterium (Azospirillum brasilense) into a heterologous Escherichia coli mutant population lacking histidine biosynthetic ability and initially unable to recognize the transcriptional signal of the introgressed gene(s). Under selective stressful conditions, His + revertants accumulated in the E. coli His − culture. The number of His + colonies was dependent on the time of incubation under selective conditions, the strength of selective pressure, and on the crowding of cells plated; moreover, it was independent of the physiological status of the cell (i.e. the growth phase). Sequence analysis of plasmid DNA extracted from E. coli His + revertants revealed that single base substitutions in the region upstream of the A. brasilense his operon resulted in an adjustment of the pre-existing sequence that was rendered similar to the E. coli −10 promoter sequence and transcriptable by the host RNA-polymerase. One particular transition (C → T) was predominant in the His + revertants. Data presented here indicated that the barriers to the expression of horizontally transferred heterologous genes or operons may be overcome in a short time scale and at high frequency, and supported the selfish operon model on the origin and evolution of gene clusters. 2001 Éditions scientifiques et médicales Elsevier SAS histidine biosynthesis / promoter-generating mutations / operon evolution / horizontal gene transfer / selfish operon * Correspondence and reprints.
1981
A restriction fragment has been isolated and its nucleotide sequence determined. This fragment contains sites for RNA polymerase binding, initiation and termination of transcription of the Escherichia coli histidine operon. In vitro transcription of plasmids containing this region generates one single histidine-specific, attenuated, small RNA: the leader RNA. This RNA is more efficiently transcribed when the template DNA is supercoiled. Another promoter was identified on the same fragment of deoxyribonucleic acid by iia vitro transcription, DNA sequencing and RNA polymerase binding. Both promoters, transcribing in opposite direction, are very AT rich and are separated by a G-C rich region containing a palyndromic structure.
Evolution of the structure and chromosomal distribution of histidine biosynthetic genes
1998
A database of more than 100 histidine biosynthetic genes from different organisms belonging to the three primary domains has been analyzed, including those found in the now completely sequenced genomes of Haemophilus influenzae, Mycoplasma genitalium, Synechocystis sp., Methanococcus jannaschii, and Saccharomyces cerevisiae. The ubiquity of his genes suggests that it is a highly conserved pathway that was probably already present in the last common ancestor of all extant life. The chromosomal distribution of the his genes shows that the enterobacterial histidine operon structure is not the only possible organization, and that there is a diversity of gene arrays for the his pathway. Analysis of the available sequences shows that gene fusions (like those involved in the origin of theEscherichia coli and Salmonella typhimurium hisIE and hisB gene structures) are not universal. In contrast, the elongation event that led to the extant hisA gene from two homologous ancestral modules, as well as the subsequent paralogous duplication that originated hisF, appear to be irreversible and are conserved in all known organisms. The available evidence supports the hypothesis that histidine biosynthesis was assembled by a gene recruitment process.
Specific binding of the first enzyme for histidine biosynthesis to the DNA of the histidine operon
Nucleic Acids Research, 1975
Studies were done to examine direct binding of the first enzyu of the histidine biosynthetic pathway (phosphoribosyltransferase) to Plabeled 80dhis DNA and competition of this binding by unlabeled homologous DNA andTiT various preparations of unlabeled heterologous DNA, including that from a defective *80 bacteriophage carrying the histidine operon with a deletion of part of its operator region. Our findings show that phosphoribosyltransferase binds specifically to a site in or near the regulatory region of the histidine operon. The stability of the complex formed by interaction of the enzyme with the DNA was markedly decreased by the substrates of the enzyme and was slightly increased by the allosteric inhibitor, histidine. These findings are consistent with previous data that indicate that phosphoribosyltransferase plays a role in regulating expression of the histidine operon.
Journal of Molecular Evolution, 1994
The hisA and hisF genes belong to the histidine operon that has been extensively studied in the enterobacteria Escherichia coli and Salmonella typhimurium where the hisA gene codes for the phosphoribosyl-5-amino-1 -phosphoribosyl-4-imidazolecarboxamide isomerase (EC 5.3.1.16) catalyzing the fourth step of the histidine biosynthetic pathway, and the hisF gene codes for a cyclase catalyzing the sixth reaction.
The Origin and Evolution of Operons: The Piecewise Building of the Proteobacterial Histidine Operon
Journal of Molecular Evolution, 2005
The structure and organization of 470 histidine biosynthetic genes from 47 different proteobacteria were combined with phylogenetic inference to investigate the mechanisms responsible for assembly of the his pathway and the origin of his operons. Data obtained in this work showed that a wide variety of different organization strategies of his gene arrays exist and that some his genes or entire his operons are likely to have been horizontally transferred between bacteria of the same or different proteobacterial branches. We propose a “piecewise” model for the origin and evolution of proteobacterial his operons, according to which the initially scattered his genes of the ancestor of proteobacteria coded for monofunctional enzymes (except possibly for hisD) and underwent a stepwise compacting process that reached its culmination in some γ-proteobacteria. The initial step of operon buildup was the formation of the his “core,” a cluster consisting of four genes (hisBHAF) whose products interconnect histidine biosynthesis to both de novo synthesis of purine metabolism and that occurred in the common ancestor of the α/β/γ branches, possibly after its separation from the ε one. The following step was the formation of three mini-operons (hisGDC, hisBHAF, hisIE) transcribed from independent promoters, that very likely occurred in the ancestor of the β/γ-branch, after its separation from the α one. Then the three mini-operons joined together to give a compact operon. In most γ-proteobacteria the two fusions involving the gene pairs hisN–B and hisI–E occurred. Finally the γ-proteobacterial his operon was horizontally transferred to other proteobacteria, such as Campylobacter jejuni. The biological significance of clustering of his genes is also discussed.
DNA sequence from the histidine operon control region: seven histidine codons in a row
Proceedings of the National Academy of Sciences, 1978
The DNA sequence of 250 base pairs preceding the first structural gene of the histidine operon of Salmonella typhimurium was determined by the dideoxy chain-termination method. Single-stranded DNA template was provided by an M13-histidine transducing phage constructed for the purpose by in vitro recombination. The termination site for the histidine leader RNA is identified by analogy with the trp operon leader termination sequence, and is 47 nucleotides before the start codon of the first structural gene G. Beginning 150 nucleotides before the end of the presumed leader RNA is a possible short protein-coding region with seven histidine codons in a row. It is proposed that the major mechanism of histodine operon control must involve a ribosome arrested at this run of histidine codons when histidine is limiting.
The Role of Gene Elongation in the Evolution of Histidine Biosynthetic Genes
Microorganisms
Gene elongation is a molecular mechanism consisting of an in-tandem duplication of a gene and divergence and fusion of the two copies, resulting in a gene constituted by two divergent paralogous modules. The aim of this work was to evaluate the importance of gene elongation in the evolution of histidine biosynthetic genes and to propose a possible evolutionary model for some of them. Concerning the genes hisA and hisF, which code for two homologous (β/α)8-barrels, it has been proposed that the two extant genes could be the result of a cascade of gene elongation/domain shuffling events starting from an ancestor gene coding for just one (β/α) module. A gene elongation event has also been proposed for the evolution of hisB and hisD; structural analyses revealed the possibility of an early elongation event, resulting in the repetition of modules. Furthermore, it is quite possible that the gene elongations responsible for the evolution of the four proteins occurred before the earliest ph...