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Quantitative Analyses of Core Promoters Enable Precise Engineering of Regulated Gene Expression in Mammalian Cells.

ABSTRACT: Inducible transcription systems play a crucial role in a wide array of synthetic biology circuits. However, the majority of inducible promoters are constructed from a limited set of tried-and-true promoter parts, which are susceptible to common shortcomings such as high basal expression levels (i.e., leakiness). To expand the toolbox for regulated mammalian gene expression and facilitate the construction of mammalian genetic circuits with precise functionality, we quantitatively characterized a panel of eight core promoters, including sequences with mammalian, viral, and synthetic origins. We demonstrate that this selection of core promoters can provide a wide range of basal gene expression levels and achieve a gradient of fold-inductions spanning 2 orders of magnitude. Furthermore, commonly used parts such as minimal CMV and minimal SV40 promoters were shown to achieve robust gene expression upon induction, but also suffer from high levels of leakiness. In contrast, a synthetic promoter, YB_TATA, was shown to combine low basal expression with high transcription rate in the induced state to achieve significantly higher fold-induction ratios compared to all other promoters tested. These behaviors remain consistent when the promoters are coupled to different genetic outputs and different response elements, as well as across different host-cell types and DNA copy numbers. We apply this quantitative understanding of core promoter properties to the successful engineering of human T cells that respond to antigen stimulation via chimeric antigen receptor signaling specifically under hypoxic environments. Results presented in this study can facilitate the design and calibration of future mammalian synthetic biology systems capable of precisely programmed functionality.

SUBMITTER: Ede C

PROVIDER: S-EPMC4874895 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Quantitative Analyses of Core Promoters Enable Precise Engineering of Regulated Gene Expression in Mammalian Cells.

Ede Christopher C Chen Ximin X Lin Meng-Yin MY Chen Yvonne Y YY

ACS synthetic biology 20160301 5

Inducible transcription systems play a crucial role in a wide array of synthetic biology circuits. However, the majority of inducible promoters are constructed from a limited set of tried-and-true promoter parts, which are susceptible to common shortcomings such as high basal expression levels (i.e., leakiness). To expand the toolbox for regulated mammalian gene expression and facilitate the construction of mammalian genetic circuits with precise functionality, we quantitatively characterized a ...[more]

PMID: 26883397

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Project description:BackgroundInducible high-level expression is favoured for recombinant protein production in Pichia pastoris. Therefore, novel regulated promoters are desired, ideally repressing heterologous gene expression during initial growth and enabling it in the production phase. In a typical large scale fed-batch culture repression is desired during the batch phase where cells grow on a surplus of e.g. glycerol, while heterologous gene expression should be active in the feed phase under carbon (e.g. glucose) limitation.ResultsDNA microarray analysis of P. pastoris wild type cells growing in glycerol-based batch and glucose-based fed batch was used for the identification of genes with both, strong repression on glycerol and high-level expression in the feed phase. Six novel glucose-limit inducible promoters were successfully applied to express the intracellular reporter eGFP. The highest expression levels together with strong repression in pre-culture were achieved with the novel promoters P(G1) and P(G6). Human serum albumin (HSA) was used to characterize the promoters with an industrially relevant secreted protein. A P(G1) clone with two gene copies reached about 230% of the biomass specific HSA titer in glucose-based fed batch fermentation compared to a P(GAP) clone with identical gene copy number, while P(G6) only achieved 39%. Two clones each carrying eleven gene copies, expressing HSA under control of P(G1) and P(G6) respectively were generated by post-transformational vector amplification. They produced about 1.0 and 0.7 g L(-1) HSA respectively in equal fed batch processes. The suitability in production processes was also verified with HyHEL antibody Fab fragment for P(G1) and with porcine carboxypeptidase B for P(G6). Moreover, the molecular function of the gene under the control of P(G1) was determined to encode a high-affinity glucose transporter and named GTH1.ConclusionsA set of novel regulated promoters, enabling induction without methanol, was successfully identified by using DNA microarrays and shown to be suitable for high level expression of recombinant proteins in glucose-based protein production processes.

Dataset Information

Quantitative Analyses of Core Promoters Enable Precise Engineering of Regulated Gene Expression in Mammalian Cells.

Publications

Quantitative Analyses of Core Promoters Enable Precise Engineering of Regulated Gene Expression in Mammalian Cells.

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