Phage-mediated Delivery of Targeted sRNA Constructs to Knock Down Gene Expression in <em>E. coli</em>

Abstract

RNA-mediated knockdowns are widely used to control gene expression. This versatile family of techniques makes use of short RNA (sRNA) that can be synthesized with any sequence and designed to complement any gene targeted for silencing. Because sRNA constructs can be introduced to many cell types directly or using a variety of vectors, gene expression can be repressed in living cells without laborious genetic modification. The most common RNA knockdown technology, RNA interference (RNAi), makes use of the endogenous RNA-induced silencing complex (RISC) to mediate sequence recognition and cleavage of the target mRNA. Applications of this technique are therefore limited to RISCexpressing organisms, primarily eukaryotes. Recently, a new generation of RNA biotechnologists have developed alternative mechanisms for controlling gene expression through RNA, and so made possible RNA-mediated gene knockdowns in bacteria. Here we describe a method for silencing gene expression in E. coli that functionally resembles RNAi. In this system a synthetic phagemid is designed to express sRNA, which may designed to target any sequence. The expression construct is delivered to a population of E. coli cells with non-lytic M13 phage, after which it is able to stably replicate as a plasmid. Antisense recognition and silencing of the target mRNA is mediated by the Hfq protein, endogenous to E. coli. This protocol includes methods for designing the antisense sRNA, constructing the phagemid vector, packaging the phagemid into M13 bacteriophage, preparing a live cell population for infection, and performing the infection itself. The fluorescent protein mKate2 and the antibiotic resistance gene chloramphenicol acetyltransferase (CAT) are targeted to generate representative data and to quantify knockdown effectiveness.

Epigenetic-Mediated Antimicrobial Resistance: Host versus Pathogen Epigenetic Alterations

“…Furthermore, with the characterization of novel ncRNAs in bacteria, targeting these ncRNA molecules might provide a promising therapeutic application against pathogens. For instance, custom ncRNA cassettes carrying the antisense sequence of a target mRNA were delivered to different E. coli strains, which helped control bacterial gene expression [ 106 ]. Another example, S. enteritica , has been reported to upregulate miR-128 expression in intestinal epithelial cells, depressing the macrophage recruitment at the site of infection.…”

Insights Into Non-coding RNAs as Novel Antimicrobial Drugs

“…Toward ncRNA-based antimicrobial therapeutics, Na et al (2013) showed that custom sRNA cassettes carrying the antisense sequence of a target mRNA and an Hfq-binding motif it is possible to modulate gene expression in different E. coli strains. Based on these findings Bernheim et al (2016) developed a protocol for synthetic sRNA delivery in E. coli cells using a phagemid construct and a non-lytic M13 phage that upon encapsulation can infect a population.…”