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Tuning the dynamic range of bacterial promoters regulated by ligand-inducible transcription factors.

ABSTRACT: One challenge for synthetic biologists is the predictable tuning of genetic circuit regulatory components to elicit desired outputs. Gene expression driven by ligand-inducible transcription factor systems must exhibit the correct ON and OFF characteristics: appropriate activation and leakiness in the presence and absence of inducer, respectively. However, the dynamic range of a promoter (i.e., absolute difference between ON and OFF states) is difficult to control. We report a method that tunes the dynamic range of ligand-inducible promoters to achieve desired ON and OFF characteristics. We build combinatorial sets of AraC-and LasR-regulated promoters containing -10 and -35 sites from synthetic and Escherichia coli promoters. Four sequence combinations with diverse dynamic ranges were chosen to build multi-input transcriptional logic gates regulated by two and three ligand-inducible transcription factors (LacI, TetR, AraC, XylS, RhlR, LasR, and LuxR). This work enables predictable control over the dynamic range of regulatory components.

SUBMITTER: Chen Y

PROVIDER: S-EPMC5754348 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Tuning the dynamic range of bacterial promoters regulated by ligand-inducible transcription factors.

Chen Ye Y Ho Joanne M L JML Shis David L DL Gupta Chinmaya C Long James J Wagner Daniel S DS Ott William W Josić Krešimir K Bennett Matthew R MR

Nature communications 20180104 1

One challenge for synthetic biologists is the predictable tuning of genetic circuit regulatory components to elicit desired outputs. Gene expression driven by ligand-inducible transcription factor systems must exhibit the correct ON and OFF characteristics: appropriate activation and leakiness in the presence and absence of inducer, respectively. However, the dynamic range of a promoter (i.e., absolute difference between ON and OFF states) is difficult to control. We report a method that tunes t ...[more]

PMID: 29302024

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Project description:BackgroundMesenchymal stromal cells (MSCs) are excessively investigated in the context of inflammation-driven diseases, but the clinical results are often moderate. MSCs are naturally activated by inflammatory signals, which lead to the secretion of immune inhibitory factors in inflamed tissues. Many work groups try to improve the therapeutic outcome of MSCs by genetic modification and the constitutive overexpression of immune modulatory transgenes. However, the ectopic secretion of immune inhibitory transgenes increases the chances of infections, and constitutive transgene expression is not necessary for chronic diseases undergoing different inflammatory stages.MethodsWe designed and tested inflammation-induced promoters to control transgene expression from integrating lentiviral vectors in human umbilical cord MSCs. Therefore, we investigated different combinations of general transcription factor elements to achieve a minimal promoter with low basal activity. The best candidates were combined with interferon-induced GAS or ISRE DNA motifs. The constructs with the highest transgene expression upon addition of pro-inflammatory cytokines were compared to vectorized promoters from inflammation-induced genes (CD317, CXCL9, CXCL10, CXCL11 and IDO1). Finally, we investigated IL10 as a potential immune inhibitory transgene by transcriptome analyses, ELISA and in an acute lung injury mouse model.ResultsThe synthetic promoters achieved a high and specific transgene expression upon IFN-γ addition. However, the CXCL11 promoter showed synergistic activity upon IFN-γ, TNF-α and IL1-β treatment and surpassed the transgene expression height of all tested promoters in the study. We observed in transcriptome analyses that IL10 has no effect on MSCs and in ELISA that IL10 is only secreted by our genetically modified and activated CXCL11-IL10-MSCs. Finally, transplanted CXCL11-IL10-MSCs increased CD19+ and CD4+ lymphoid cells, and decreased CD11b+ Ly6g myeloid cells in an ALI mouse model.ConclusionThese results provide new insights into MSC inflammatory activation and the subsequent translation into a tool for a tailored expression of transgenes in inflammatory microenvironments. The newly developed promoter elements are potentially interesting for other inflamed tissues, and can be combined with other elements or used in other cell types.

Dataset Information

Tuning the dynamic range of bacterial promoters regulated by ligand-inducible transcription factors.

Publications

Tuning the dynamic range of bacterial promoters regulated by ligand-inducible transcription factors.

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