Abstract
MicroRNAs (miRNAs) are small non-coding RNAs that play important roles in many biological processes such as development, cell signaling and immune response. Small RNA deep sequencing technology provided an opportunity for a thorough survey of the miRNA profile of a mosquito cell line from Aedes aegypti. We characterized the miRNA composition of the nucleus and the cytoplasm of uninfected cells and compared it with the one of cells infected with the endosymbiotic bacterium Wolbachia strain wMelPop-CLA. We found an overall increase of small RNAs between 18 and 28 nucleotides in both cellular compartments in Wolbachia-infected cells and identified specific miRNAs induced and/or suppressed by the Wolbachia infection. We discuss the mechanisms that the cell may use to shuttle miRNAs between the cytoplasm and the nucleus. In addition, we identified piRNAs that changed their abundance in response to Wolbachia infection. The miRNAs and piRNAs identified in this study provide promising leads for investigations into the host-endosymbiont interactions and for better understanding of how Wolbachia manipulates the host miRNA machinery in order to facilitate its persistent replication in infected cells.
Highlights
MicroRNAs are small non-coding RNAs of,22 nucleotides produced by animals and plants as well as some viruses. miRNAs may be encoded from non-coding transcripts, introns or even coding regions. miRNA genes are expressed mainly by RNA polymerase II in the nucleus as primary miRNA [1,2]. pri-miRNA is cleaved by Drosha to a 60- to 80-nt precursor miRNA with multiple mismatches and bulges, which is exported by Exportin-5 to the cytoplasm and cleaved by Dicer-1, generating an approximately 22-nt double-stranded miRNA
This study found an overall increase for small RNAs between 18 and 28 nucleotides in cells infected with the endosymbiontic bacterium Wolbachia strain wMelPop-CLA, and an increase in the mRNA levels of the argonaute proteins AGO1–3
Wolbachia changed the abundance of specific sets of miRNAs in the nucleus and the cytoplasm of mosquito cells and altered the natural miRNA profile of Aag2 cells
Summary
MicroRNAs (miRNAs) are small non-coding RNAs of ,22 nucleotides (nt) produced by animals and plants as well as some viruses. miRNAs may be encoded from non-coding transcripts, introns or even coding regions. miRNA genes are expressed mainly by RNA polymerase II in the nucleus as primary miRNA (pri-miRNA) [1,2]. pri-miRNA is cleaved by Drosha to a 60- to 80-nt precursor miRNA (pre-miRNA) with multiple mismatches and bulges, which is exported by Exportin-5 to the cytoplasm and cleaved by Dicer-1, generating an approximately 22-nt double-stranded miRNA (miRNA-5p: miRNA-3p duplex). In the last few years, investigators have studied the involvement of miRNAs in host-pathogen interactions This involvement is well established, but the amount of studies in insects is limited. Their role has been shown by disrupting the biosynthesis of host miRNAs, inhibiting specific miRNAs or by studying the miRNA profile of the host before and after infection [6]. These changes in the miRNA levels may be induced by pathogen-derived components (including their own miRNAs) or as an immune response mechanism to infection [1]
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