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The novel cis-encoded antisense RNA AsrC positively regulates the expression of rpoE-rseABC operon and thus enhances the motility of Salmonella enterica serovar typhi.

Zhang Q, Zhang Y, Zhang X, Zhan L, Zhao X, Xu S, Sheng X, Huang X - Front Microbiol (2015)

Bottom Line: We found that AsrC increased the levels of rseC mRNA and protein.The expression of rpoE was also increased in S. typhi after overexpression of AsrC, which was dependent on rseC.Thus, we propose that AsrC increased RseC level and indirectly activating RpoE which can initiate fliA expression and promote the motility of S. typhi.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, Jiangsu University - School of Medicine Zhenjiang, China ; Danyang People's Hospital of Jiangsu Province Danyang, China.

ABSTRACT
Bacterial non-coding RNAs are essential in many cellular processes, including response to environmental stress, and virulence. Deep sequencing analysis of the Salmonella enterica serovar typhi (S. typhi) transcriptome revealed a novel antisense RNA transcribed in cis on the strand complementary to rseC, an activator gene of sigma factor RpoE. In this study, expression of this antisense RNA was confirmed in S. typhi by Northern hybridization. Rapid amplification of cDNA ends and sequence analysis identified an 893 bp sequence from the antisense RNA coding region that covered all of the rseC coding region in the reverse direction of transcription. This sequence of RNA was named as AsrC. After overexpression of AsrC with recombinantant plasmid in S. typhi, the bacterial motility was increased obviously. To explore the mechanism of AsrC function, regulation of rseC and rpoE expression by AsrC was investigated. We found that AsrC increased the levels of rseC mRNA and protein. The expression of rpoE was also increased in S. typhi after overexpression of AsrC, which was dependent on rseC. Thus, we propose that AsrC increased RseC level and indirectly activating RpoE which can initiate fliA expression and promote the motility of S. typhi.

No MeSH data available.


AsrC and its regulatory circuits. AsrC expression increases rseC mRNA and protein levels. RseC positively modulates transcriptional activity of rpoE and increases RpoE (σE) protein. The rpoE gene is positively autoregulated. Enhanced σE regulatory pathways respond by inducing transcription of genes related to motility. Arrows, activation.
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Figure 8: AsrC and its regulatory circuits. AsrC expression increases rseC mRNA and protein levels. RseC positively modulates transcriptional activity of rpoE and increases RpoE (σE) protein. The rpoE gene is positively autoregulated. Enhanced σE regulatory pathways respond by inducing transcription of genes related to motility. Arrows, activation.

Mentions: The protein σE is involved in the response to extracytoplasmic stresses and initiates transcription of a series of genes in Escherichia and Salmonella under environmental stress, for example, high osmolarity and oxidative stress (Testerman et al., 2002; Miticka et al., 2003; Rolhion et al., 2007). In our study, AsrC overexpression increased rpoE mRNA and protein, probably by enhancing transcription and translation of rseC (Figure 6). RseC protein began to increase after 0.5 h of AsrC induction and RpoE increased after 2 h of induction, 1.5 h later than RseC. Increased RpoE protein appeared later than RseC protein, suggesting that AsrC induced RpoE expression through enhancing expression of RseC. Our results showed that AsrC was expressed throughout S. typhi growth, with the highest expression during late exponential phase (Figure 2), and rpoE mRNA were increased ∼16-fold during the transition to stationary phase (Testerman et al., 2002). The enhancement of rpoE expression could be partly due to increased expression of asrC mRNA, which is resulted in an increase in rseC expression. In our observation, overexpression of AsrC in an rseC mutant strain had no significant effect on rpoE mRNA and protein (Figure 7). Thus, we hypothesized a pathway in which AsrC overexpression increased rpoE expression primarily through increasing expression of rseC and enhanced σE regulatory pathways. Moreover, it is known that at the transcriptional level, the rpoE gene is positively autoregulated, because one of its own promoters is transcribed by the EσE holoenzyme itself (Raina et al., 1995; Rouvière et al., 1995). Therefore, by increasing the expression of RseC that positively controls RpoE activity, AsrC could induces the expression of the rpoE-rseABC operon. Taken together, AsrC promoted the expression of genes related to motility and enhancing the motility of S. typhi (Figure 8).


The novel cis-encoded antisense RNA AsrC positively regulates the expression of rpoE-rseABC operon and thus enhances the motility of Salmonella enterica serovar typhi.

Zhang Q, Zhang Y, Zhang X, Zhan L, Zhao X, Xu S, Sheng X, Huang X - Front Microbiol (2015)

AsrC and its regulatory circuits. AsrC expression increases rseC mRNA and protein levels. RseC positively modulates transcriptional activity of rpoE and increases RpoE (σE) protein. The rpoE gene is positively autoregulated. Enhanced σE regulatory pathways respond by inducing transcription of genes related to motility. Arrows, activation.
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Figure 8: AsrC and its regulatory circuits. AsrC expression increases rseC mRNA and protein levels. RseC positively modulates transcriptional activity of rpoE and increases RpoE (σE) protein. The rpoE gene is positively autoregulated. Enhanced σE regulatory pathways respond by inducing transcription of genes related to motility. Arrows, activation.
Mentions: The protein σE is involved in the response to extracytoplasmic stresses and initiates transcription of a series of genes in Escherichia and Salmonella under environmental stress, for example, high osmolarity and oxidative stress (Testerman et al., 2002; Miticka et al., 2003; Rolhion et al., 2007). In our study, AsrC overexpression increased rpoE mRNA and protein, probably by enhancing transcription and translation of rseC (Figure 6). RseC protein began to increase after 0.5 h of AsrC induction and RpoE increased after 2 h of induction, 1.5 h later than RseC. Increased RpoE protein appeared later than RseC protein, suggesting that AsrC induced RpoE expression through enhancing expression of RseC. Our results showed that AsrC was expressed throughout S. typhi growth, with the highest expression during late exponential phase (Figure 2), and rpoE mRNA were increased ∼16-fold during the transition to stationary phase (Testerman et al., 2002). The enhancement of rpoE expression could be partly due to increased expression of asrC mRNA, which is resulted in an increase in rseC expression. In our observation, overexpression of AsrC in an rseC mutant strain had no significant effect on rpoE mRNA and protein (Figure 7). Thus, we hypothesized a pathway in which AsrC overexpression increased rpoE expression primarily through increasing expression of rseC and enhanced σE regulatory pathways. Moreover, it is known that at the transcriptional level, the rpoE gene is positively autoregulated, because one of its own promoters is transcribed by the EσE holoenzyme itself (Raina et al., 1995; Rouvière et al., 1995). Therefore, by increasing the expression of RseC that positively controls RpoE activity, AsrC could induces the expression of the rpoE-rseABC operon. Taken together, AsrC promoted the expression of genes related to motility and enhancing the motility of S. typhi (Figure 8).

Bottom Line: We found that AsrC increased the levels of rseC mRNA and protein.The expression of rpoE was also increased in S. typhi after overexpression of AsrC, which was dependent on rseC.Thus, we propose that AsrC increased RseC level and indirectly activating RpoE which can initiate fliA expression and promote the motility of S. typhi.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, Jiangsu University - School of Medicine Zhenjiang, China ; Danyang People's Hospital of Jiangsu Province Danyang, China.

ABSTRACT
Bacterial non-coding RNAs are essential in many cellular processes, including response to environmental stress, and virulence. Deep sequencing analysis of the Salmonella enterica serovar typhi (S. typhi) transcriptome revealed a novel antisense RNA transcribed in cis on the strand complementary to rseC, an activator gene of sigma factor RpoE. In this study, expression of this antisense RNA was confirmed in S. typhi by Northern hybridization. Rapid amplification of cDNA ends and sequence analysis identified an 893 bp sequence from the antisense RNA coding region that covered all of the rseC coding region in the reverse direction of transcription. This sequence of RNA was named as AsrC. After overexpression of AsrC with recombinantant plasmid in S. typhi, the bacterial motility was increased obviously. To explore the mechanism of AsrC function, regulation of rseC and rpoE expression by AsrC was investigated. We found that AsrC increased the levels of rseC mRNA and protein. The expression of rpoE was also increased in S. typhi after overexpression of AsrC, which was dependent on rseC. Thus, we propose that AsrC increased RseC level and indirectly activating RpoE which can initiate fliA expression and promote the motility of S. typhi.

No MeSH data available.