A Small Non-Coding RNA Modulates Expression of Pilus-1 Type in Streptococcus pneumoniae

Abstract

Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide, and about 30% of the pneumococcal clinical isolates show type I pili-like structures. These long proteinaceous polymers extending from the bacterial surface are encoded by pilus islet 1 and play major roles in adhesion and host colonization. Pili expression is bistable and is controlled by the transcriptional activator RlrA. In this work, we demonstrate that the previously identified small noncoding RNA srn135 also participates in pilus regulation. Our findings show that srn135 is generated upon processing of the 5′-UTR region of rrgA messenger and its deletion prevents the synthesis of RrgA, the main pili adhesin. Moreover, overexpression of srn135 increases the expression of all pili genes and rises the percentage of piliated bacteria within a clonal population. This regulation is mediated by the stabilization of rlrA mRNA since higher levels of srn135 increase its half-life to 165%. Our findings suggest that srn135 has a dual role in pilus expression acting both in cis- (on the RrgA levels) and in trans- (modulating the levels of RlrA) and contributes to the delicate balance between pili expressing and non-expressing bacteria.

Role of PatAB Transporter in Efflux of Levofloxacin in Streptococcus pneumoniae

“…RNA integrity was evaluated by gel electrophoresis and its concentration determined using a Nanodrop 1000 spectrophotometer (Nanodrop Technologies). Reverse transcription reactions were performed with the SuperScript III First-Strand Synthesis System for RT-qPCR (Invitrogen) using 2 µg of total RNA and 50 ng/µL of random hexamers, as previously described [ 52 ]. A mock cDNA synthesis reaction was performed, with the reverse transcriptase replaced by water.…”

Small noncoding RNA in Streptococci: From regulatory functions to drug development

“…pneumoniae plays a dual regulatory role in both cis-and trans-mode in the expression of pilus (Acebo et al, 2021). The activation of srn135 could increase the expression of all pili genes and the percentage of piliated bacteria under transmission electron microscopy by increasing the protein levels of downstream rrgA in a cis-regulatory mode and stabilizing the mRNA of upstream rlrA in a trans-regulatory mode (Acebo et al, 2021). Although the precise regulatory mechanism of srn135 in pilus islet needs to be elucidated in the future studies, this study provided us new perspectives about the riboregulatory roles of sRNA in bacteria.…”

“…An unclassified sRNA srn135 from S. pneumoniae plays a dual regulatory role in both cis ‐ and trans ‐mode in the expression of pilus (Acebo et al., 2021). The activation of srn135 could increase the expression of all pili genes and the percentage of piliated bacteria under transmission electron microscopy by increasing the protein levels of downstream rrgA in a cis ‐regulatory mode and stabilizing the mRNA of upstream rlrA in a trans ‐regulatory mode (Acebo et al., 2021). Although the precise regulatory mechanism of srn135 in pilus islet needs to be elucidated in the future studies, this study provided us new perspectives about the riboregulatory roles of sRNA in bacteria.…”

Developing New Tools to Fight Human Pathogens: A Journey through the Advances in RNA Technologies

“…In Streptococcus pneumoniae, a significant percentage from the identified ncRNAs has important roles in virulence traits [82]. srn157 and F32 were shown to be important for the adhesion/invasion of endothelial or nasopharyngeal cells [83,84], five redundant csRNAs (cis-dependent small RNAs) together with the ncRNA srn206 act to modulate competence [85], and srn135 was demonstrated to be involved in pilus regulation [86].…”