A Direct RNA-to-RNA Replication System for Enhanced Gene Expression in Bacteria.

A long-standing objective of metabolic engineering has been to exogenously increase the expression of target genes. In this research, we proposed the permanent RNA replication system using DNA as a template to store genetic information in bacteria. We selected Qβ phage as the RNA replication prototype and made many improvements to achieve target gene expression enhancement directly by increasing mRNA abundance. First, we identified the endogenous gene Rnc, the knockout of which significantly improved the RNA replication efficiency. Second, we elucidated the essential elements for RNA replication and optimized the system to make it more easily applicable. Combined with optimization of the host cell and the system itself, we developed a stable RNA-to-RNA replication tool to directly increase the abundance of the target mRNA and subsequently the target protein. Furthermore, it was proven efficient in enhancing the expression of specific proteins and was demonstrated to be applicable in metabolic engineering. Our system has the potential to be combined with any of the existing methods for increasing gene expression.