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Published December 2000 | Published
Journal Article Open

Coordinated, Differential Expression of Two Genes through Directed mRNA Cleavage and Stabilization by Secondary Structures


Metabolic engineering and multisubunit protein production necessitate the expression of multiple genes at coordinated levels. In bacteria, genes for multisubunit proteins or metabolic pathways are often expressed in operons under the control of a single promoter; expression of the genes is coordinated by varying transcript stability and the rate of translation initiation. We have developed a system to place multiple genes under the control of a single promoter and produce proteins encoded in that novel operon in different ratios over a range of inducer concentrations. RNase E sites identified in the Rhodobacter capsulatus puf operon and Escherichia coli pap operon were separately placed between the coding regions of two reporter genes, and novel secondary structures were engineered into the 5' and 3' ends of the coding regions. The introduced RNase E site directed cleavage between the coding regions to produce two secondary transcripts, each containing a single coding region. The secondary transcripts were protected from exonuclease cleavage by engineered 3' secondary structures, and one of the secondary transcripts was protected from RNase E cleavage by secondary structures at the 5' end. The relative expression levels of two reporter genes could be varied up to fourfold, depending on inducer concentration, by controlling RNase cleavage of the primary and secondary transcripts. Coupled with the ability to vary translation initiation by changing the ribosome binding site, this technology should allow one to create new operons and coordinate, yet separately control, the expression levels of genes expressed in that operon.

Additional Information

© 2000, American Society for Microbiology. All rights reserved. Received 14 July 2000/Accepted 29 September 2000 We thank N. Pace and S. Kustu for their help with the primer extension work and C. Bertozzi and P. Schultz for use of their PhosphorImager. This research was supported in part by the ERC Program of the National Science Foundation under award number EEC-9731725, National Science Foundation grants BES-9502495 and BES-9906405, and a National Science Foundation graduate fellowship to C. D. Smolke.

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