Acis-regulatory antisense RNA represses translation inVibrio choleraethrough extensive complementarity and proximity to the target locus

Abstract

As with all facultative pathogens, Vibrio cholerae must optimize its cellular processes to adapt to different environments with varying carbon sources and to environmental stresses. More specifically, in order to metabolize mannitol, V. cholerae must regulate the synthesis of MtlA, a mannitol transporter protein produced exclusively in the presence of mannitol. We previously showed that a cis-acting small RNA (sRNA) expressed by V. cholerae, MtlS, appears to post-transcriptionally downregulate the expression of mtlA and is produced in the absence of mannitol. We hypothesized that since it is complementary to the 5′ untranslated region (UTR) of mtlA mRNA, MtlS may affect synthesis of MtlA by forming an mtlA-MtlS complex that blocks translation of the mRNA through occlusion of its ribosome binding site. To test this hypothesis, we used in vitro translation assays in order to examine the role MtlS plays in mtlA regulation and found that MtlS is sufficient to suppress translation of transcripts harboring the 5′ UTR of mtlA. However, in a cellular context, the 5′ UTR of mtlA is not sufficient for targeted repression by endogenous MtlS; additional segments from the coding region of mtlA play a role in the ability of the sRNA to regulate translation of mtlA mRNA. Additionally, proximity of transcription sites between the sRNA and mRNA significantly affects the efficacy of MtlS.

Role of Non-coding Regulatory RNA in the Virulence of Human Pathogenic Vibrios

“…In case of sRNA- trans , a single mRNA can be regulated by more than one sRNA (Bardill and Hammer, 2012; Duval et al, 2014; Chang et al, 2015). This type of sRNA has been more widely studied and is the most abundant type of sRNA discovered to date.…”

“…Their size also varies from approximately 100 to more than 300 nt, and may overlap with the 5′ or 3′ ends or be in a middle zone of the gene coded opposite the sRNA (Chang et al, 2015). These sRNAs are located in the antisense strand of their target RNA regions and their mechanism of action leads to the post-transcriptional down-regulation of the target gene through perfect extended duplex (Oliva et al, 2015).…”

“…Full and lengthy complementarity between the sRNA and its target, observed in sRNA- cis , can lead to very stable duplexes, allowing regulation that is independent of proteins such as Hfq (Chang et al, 2015). Also, the cis position has the effect that sRNA and target are transcribed in close proximity, which can facilitate and improve interactions between the regulator molecules and their objective (Georg and Hess, 2011; Chang et al, 2015). …”

COLRAcinetobacter baumannii sRNA Signatures: Computational Comparative Identification and Biological Targets

“…Conversely, cis-acting sRNAs are transcribed from the same genetic locus that they regulate even thought in an antisense orientation to the target gene. Since transcribed proximally to their target, cis-antisense RNAs share a perfect match with their targets allowing duplex formation and a stringent regulation (Thomason and Storz, 2010;Chang et al, 2015;Georg and Hess, 2018).…”

MtlR negatively regulates mannitol utilization by Vibrio cholerae

“…This regulator is activated by cAMP to directly bind five distinct sites found in the mtlA promoter and is necessary for activation of mtlA [ 26 ]. Recent studies further demonstrate that mtlA expression in V. cholerae is negatively regulated by MtlS, a cis -acting small regulatory RNA (sRNA) [ 27, 28 ]. One of the least characterized regulators of mtlA in V. cholerae , however, is MtlR.…”