A mobile genetic element with unknown function found in distantly related viruses

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Abstract

Background

The genetic element s2m seems to represent one of very few examples of mobile genetic elements in viruses. The function remains obscure and a scattered taxonomical distribution has been reported by numerous groups.

Methods

We have searched GenBank in order to identify all viral accessions that have s2m(−like) sequence motifs. Rigorous phylogenetic analyses and constrained tree topology testing were also performed in order to investigate the apparently mobile nature of s2m.

Results

The stem-loop s2m structure can be found in four families of + ssRNA viruses; Astroviridae, Caliciviridae, Picornaviridae and Coronaviridae. In all of these virus families, with the possible exception of Caliciviridae, multiple gains and/or losses of s2m would have to be postulated in order to explain the distribution of this character.

Conclusions

s2m appears to be a mobile genetic element with a unique evolutionary history in all of the four virus families where it can be found. Based on our findings and a review of the current literature on s2m, a hypothesis implying an RNAi-like function for the s2m element is also outlined.

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Most cited references 13

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Discovery of seven novel Mammalian and avian coronaviruses in the genus deltacoronavirus supports bat coronaviruses as the gene source of alphacoronavirus and betacoronavirus and avian coronaviruses as the gene source of gammacoronavirus and deltacoronavirus.

P Woo, S K P Lau, C. S. F. Lam … (2012)

Recently, we reported the discovery of three novel coronaviruses, bulbul coronavirus HKU11, thrush coronavirus HKU12, and munia coronavirus HKU13, which were identified as representatives of a novel genus, Deltacoronavirus, in the subfamily Coronavirinae. In this territory-wide molecular epidemiology study involving 3,137 mammals and 3,298 birds, we discovered seven additional novel deltacoronaviruses in pigs and birds, which we named porcine coronavirus HKU15, white-eye coronavirus HKU16, sparrow coronavirus HKU17, magpie robin coronavirus HKU18, night heron coronavirus HKU19, wigeon coronavirus HKU20, and common moorhen coronavirus HKU21. Complete genome sequencing and comparative genome analysis showed that the avian and mammalian deltacoronaviruses have similar genome characteristics and structures. They all have relatively small genomes (25.421 to 26.674 kb), the smallest among all coronaviruses. They all have a single papain-like protease domain in the nsp3 gene; an accessory gene, NS6 open reading frame (ORF), located between the M and N genes; and a variable number of accessory genes (up to four) downstream of the N gene. Moreover, they all have the same putative transcription regulatory sequence of ACACCA. Molecular clock analysis showed that the most recent common ancestor of all coronaviruses was estimated at approximately 8100 BC, and those of Alphacoronavirus, Betacoronavirus, Gammacoronavirus, and Deltacoronavirus were at approximately 2400 BC, 3300 BC, 2800 BC, and 3000 BC, respectively. From our studies, it appears that bats and birds, the warm blooded flying vertebrates, are ideal hosts for the coronavirus gene source, bats for Alphacoronavirus and Betacoronavirus and birds for Gammacoronavirus and Deltacoronavirus, to fuel coronavirus evolution and dissemination.

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Bacteriophages and their genomes.

Graham F. Hatfull, C Hendrix (2011)

Bacteriophages occupy a unique position in biology, representing an absolute majority of all organisms in the biosphere. Because their genomes are relatively small, elucidating the genetic diversity of the phage population, deciphering their origins, and identifying the evolutionary mechanisms that shape the population would seem readily feasible. And yet the pace of phage genome characterization has slowed over the past three years, reflecting in part a need to transition from sequencing known and well-characterized bacteriophages to the isolation and comparative analysis of new isolates. The current state of bacteriophage genomics shows that the genetic diversity of the population is very high, that phages have been actively evolving for billions of years with active engagement of horizontal genetic exchange, and that their genomes are consequently pervasively mosaic in their architectures. But we have barely scratched the surface and the next years of phage genome exploration promise to be especially revealing.

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A common RNA motif in the 3' end of the genomes of astroviruses, avian infectious bronchitis virus and an equine rhinovirus.

B Grinde, T Jonassen, Else M. Jonassen (1998)

In the 3' non-coding region of the genomes of infectious bronchitis virus, an avian coronavirus and the picornavirus equine rhinovirus serotype 2, there is a motif with remarkable similarity, both in sequence and folding, to the second RNA stem-loop from the 3' end of the genomes of human astroviruses. This motif was also found in astroviruses of sheep, pig and turkey, suggesting that it is a common feature of all astroviruses. The conserved nature of the motif indicates that there has been strong selection for its preservation. There is significant homology between the regions flanking this motif in infectious bronchitis virus and a continuous RNA sequence at the same distance from the 3' poly(A) tail in some related mammalian coronaviruses. These observations suggest that the presence of the motif in these three viral families is the result of at least two separate RNA recombination events.

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Author and article information

Journal

Journal ID (nlm-ta): Virol J

Journal ID (iso-abbrev): Virol. J

Title: Virology Journal

Publisher: BioMed Central

ISSN (Electronic): 1743-422X

Publication date Collection: 2013

Publication date (Electronic): 25 April 2013

Volume: 10

Page: 132

Affiliations

[1 ]National Veterinary Institute, P.O. Box 750 Sentrum, 0106, Oslo, Norway

[2 ]Institute for Marine and Environmental Technology, 701 E. Pratt St, Baltimore, MD 21202, USA

Article

Publisher ID: 1743-422X-10-132

DOI: 10.1186/1743-422X-10-132

PMC ID: 3653767

PubMed ID: 23618040

SO-VID: dee18151-7fce-4742-9f8c-0bd45db3cb15

License:

This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

A mobile genetic element with unknown function found in distantly related viruses

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Abstract

Background

Methods

Results

Conclusions

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Microbiology Society: Coronaviruses

Most cited references 13

Discovery of seven novel Mammalian and avian coronaviruses in the genus deltacoronavirus supports bat coronaviruses as the gene source of alphacoronavirus and betacoronavirus and avian coronaviruses as the gene source of gammacoronavirus and deltacoronavirus.

Bacteriophages and their genomes.

A common RNA motif in the 3' end of the genomes of astroviruses, avian infectious bronchitis virus and an equine rhinovirus.

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