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Open Access Highly Accessed Research article

Identification of CRISPR and riboswitch related RNAs among novel noncoding RNAs of the euryarchaeon Pyrococcus abyssi

Kounthéa Phok12, Annick Moisan2, Dana Rinaldi1, Nicolas Brucato13, Agamemnon J Carpousis1, Christine Gaspin2* and Béatrice Clouet-d'Orval1*

Author Affiliations

1 Laboratoire de Microbiologie et Génétique Moléculaire, UMR 5100, Centre National de la Recherche Scientifique et Université de Toulouse III, 31062 Toulouse, France

2 Laboratoire d'Intelligence artificielle, UR 875-INRA, 31326 Auzeville-Tolosan, France

3 Laboratoire d'Anthropobiologie Moléculaire et Imagerie de Synthèse, UMR 5288, Centre National de la Recherche Scientifique, 31073 Toulouse, France

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BMC Genomics 2011, 12:312  doi:10.1186/1471-2164-12-312

Published: 13 June 2011

Abstract

Background

Noncoding RNA (ncRNA) has been recognized as an important regulator of gene expression networks in Bacteria and Eucaryota. Little is known about ncRNA in thermococcal archaea except for the eukaryotic-like C/D and H/ACA modification guide RNAs.

Results

Using a combination of in silico and experimental approaches, we identified and characterized novel P. abyssi ncRNAs transcribed from 12 intergenic regions, ten of which are conserved throughout the Thermococcales. Several of them accumulate in the late-exponential phase of growth. Analysis of the genomic context and sequence conservation amongst related thermococcal species revealed two novel P. abyssi ncRNA families. The CRISPR family is comprised of crRNAs expressed from two of the four P. abyssi CRISPR cassettes. The 5'UTR derived family includes four conserved ncRNAs, two of which have features similar to known bacterial riboswitches. Several of the novel ncRNAs have sequence similarities to orphan OrfB transposase elements. Based on RNA secondary structure predictions and experimental results, we show that three of the twelve ncRNAs include Kink-turn RNA motifs, arguing for a biological role of these ncRNAs in the cell. Furthermore, our results show that several of the ncRNAs are subjected to processing events by enzymes that remain to be identified and characterized.

Conclusions

This work proposes a revised annotation of CRISPR loci in P. abyssi and expands our knowledge of ncRNAs in the Thermococcales, thus providing a starting point for studies needed to elucidate their biological function.