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Dual transcriptional-translational cascade permits cellular level tuneable expression control.

ABSTRACT: The ability to induce gene expression in a small molecule dependent manner has led to many applications in target discovery, functional elucidation and bio-production. To date these applications have relied on a limited set of protein-based control mechanisms operating at the level of transcription initiation. The discovery, design and reengineering of riboswitches offer an alternative means by which to control gene expression. Here we report the development and characterization of a novel tunable recombinant expression system, termed RiboTite, which operates at both the transcriptional and translational level. Using standard inducible promoters and orthogonal riboswitches, a multi-layered modular genetic control circuit was developed to control the expression of both bacteriophage T7 RNA polymerase and recombinant gene(s) of interest. The system was benchmarked against a number of commonly used E. coli expression systems, and shows tight basal control, precise analogue tunability of gene expression at the cellular level, dose-dependent regulation of protein production rates over extended growth periods and enhanced cell viability. This novel system expands the number of E. coli expression systems for use in recombinant protein production and represents a major performance enhancement over and above the most widely used expression systems.

SUBMITTER: Morra R

PROVIDER: S-EPMC4756846 | biostudies-other | 2016 Feb

REPOSITORIES: biostudies-other

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Dual transcriptional-translational cascade permits cellular level tuneable expression control.

Morra Rosa R Shankar Jayendra J Robinson Christopher J CJ Halliwell Samantha S Butler Lisa L Upton Mathew M Hay Sam S Micklefield Jason J Dixon Neil N

Nucleic acids research 20150923 3

The ability to induce gene expression in a small molecule dependent manner has led to many applications in target discovery, functional elucidation and bio-production. To date these applications have relied on a limited set of protein-based control mechanisms operating at the level of transcription initiation. The discovery, design and reengineering of riboswitches offer an alternative means by which to control gene expression. Here we report the development and characterization of a novel tunab ...[more]

PMID: 26405200

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Project description:BACKGROUND:The genome-integrated T7 expression system offers significant advantages, in terms of productivity and product quality, even when expressing the gene of interest (GOI) from a single copy. Compared to plasmid-based expression systems, this system does not incur a plasmid-mediated metabolic load, and it does not vary the dosage of the GOI during the production process. However, long-term production with T7 expression system leads to a rapidly growing non-producing population, because the T7 RNA polymerase (RNAP) is prone to mutations. The present study aimed to investigate whether two ?70 promoters, which were recognized by the Escherichia coli host RNAP, might be suitable in genome-integrated expression systems. We applied a promoter engineering strategy that allowed control of expressing the model protein, GFP, by introducing lac operators (lacO) into the constitutive T5 and A1 promoter sequences. RESULTS:We showed that, in genome-integrated E. coli expression systems that used ?70 promoters, the number of lacO sites must be well balanced. Promoters containing three and two lacO sites exhibited low basal expression, but resulted in a complete stop in recombinant protein production in partially induced cultures. In contrast, expression systems regulated by a single lacO site and the lac repressor element, lacIQ, on the same chromosome caused very low basal expression, were highly efficient in recombinant protein production, and enables fine-tuning of gene expression levels on a cellular level. CONCLUSIONS:Based on our results, we hypothesized that this phenomenon was associated with the autoregulation of the lac repressor protein, LacI. We reasoned that the affinity of LacI for the lacO sites of the GOI must be lower than the affinity of LacI to the lacO sites of the endogenous lac operon; otherwise, LacI autoregulation could not take place, and the lack of LacI autoregulation would lead to a disturbance in lac repressor-mediated regulation of transcription. By exploiting the mechanism of LacI autoregulation, we created a novel E. coli expression system for use in recombinant protein production, synthetic biology, and metabolic engineering applications.

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Dual transcriptional-translational cascade permits cellular level tuneable expression control.

Publications

Dual transcriptional-translational cascade permits cellular level tuneable expression control.

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