Construction of a host-independent T7 expression system with small RNA regulation

Customized design of host-independent T7 expression system (HITES) for a broad host range

Efficient methods and universal DNA elements are eagerly required for the expression of proteins and the production of target chemicals in synthetic biology and metabolic engineering. This paper develops a customized-design approach by utilizing the host-independent T7 expression system (HITES), which facilitates the rational design and rapid construction of T7 expression systems. Firstly, the EiL (Upper-limit value of initial enzyme activity) value is discovered to play a pivotal factor in the successful construction of the T7 expression system, different host strains exhibit varying EiL values, and this study presents a method to measure the EiL values. Secondly, E. coli DH5α is chosen as the host strain, and it demonstrates that various strategies to modulate T7 RNA polymerase activity can efficiently construct the HITES T7 expression system in E. coli DH5α under the guidance of EiL. Lastly, the customized-design of HITES enables the efficient expression of sfGFP and D-MIase proteins across 13 host strains, guided by EiL values. This customized-design method of HITES offers a streamlined pathway for T7 system construction across a broad range of hosts and serves as an enabling tool for synthetic biology, metabolic engineering, and enzyme engineering.

Integrating T7 RNA Polymerase and Its Cognate Transcriptional Units for a Host-Independent and Stable Expression System in Single Plasmid

Metabolic engineering and synthetic biology usually require universal expression systems for stable and efficient gene expression in various organisms. In this study, a host-independent and stable T7 expression system had been developed by integrating T7 RNA polymerase and its cognate transcriptional units in single plasmid. The expression of T7 RNA polymerase was restricted below its lethal threshold using a T7 RNA polymerase antisense gene cassette, which allowed long periods of cultivation and protein production. In addition, by designing ribosome binding sites, we further tuned the expression capacity of this novel T7 system within a wide range. This host-independent expression system efficiently expressed genes in five different Gram-negative strains and one Gram-positive strain and was also shown to be applicable in a real industrial d- p-hydroxyphenylglycine production system.