Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2012 Aug 14;109(33):13386-91.
doi: 10.1073/pnas.1203668109. Epub 2012 Jul 23.

Archaeal Virus With Exceptional Virion Architecture and the Largest Single-Stranded DNA Genome

Affiliations
Free PMC article

Archaeal Virus With Exceptional Virion Architecture and the Largest Single-Stranded DNA Genome

Tomohiro Mochizuki et al. Proc Natl Acad Sci U S A. .
Free PMC article

Abstract

Known viruses build their particles using a restricted number of redundant structural solutions. Here, we describe the Aeropyrum coil-shaped virus (ACV), of the hyperthermophilic archaeon Aeropyrum pernix, with a virion architecture not previously observed in the viral world. The nonenveloped, hollow, cylindrical virion is formed from a coiling fiber, which consists of two intertwining halves of a single circular nucleoprotein. The virus ACV is also exceptional for its genomic properties. It is the only virus with a single-stranded (ss) DNA genome among the known hyperthermophilic archaeal viruses. Moreover, the size of its circular genome, 24,893 nt, is double that of the largest known ssDNA genome, suggesting an efficient solution for keeping ssDNA intact at 90-95 °C, the optimal temperature range of A. pernix growth. The genome content of ACV is in line with its unique morphology and confirms that ACV is not closely related to any known virus.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Electron micrographs of ACV virions. (A and B) Negatively stained with 2% (wt/vol) uranyl acetate. (C and D) Sample embedded in vitreous ice. (Scale bars, 100 nm.)
Fig. 2.
Fig. 2.
Comparison of ACV to other helical viruses. Portions of negatively stained virions of ACV, tobacco mosaic virus (TMV), and Sulfolobus islandicus rod-shaped virus 2 (SIRV2) are in the left column, and their cryo-EM images are in the right column. Original micrographs are shown in Fig. S3. The pitch of the virion helix, determined by Fourier transformation of the negatively stained images, is indicated.
Fig. 3.
Fig. 3.
Transmission electron micrographs of disrupted ACV virions. (A) Fragments of partially disassembled virions connected by a twisted filament. (B) A completely unwound helix-forming filament; the regions where two constituent strands of the helix-forming filament are clearly distinguishable are shown in Insets and are indicated by arrowheads. [Scale bars: (A) 200 nm; (B) 500 nm; (Insets) 100 nm.]
Fig. 4.
Fig. 4.
Analysis of single-stranded DNA orientation. Agarose gel electrophoresis of PCR products after step 2 of the Strand Orientation–SISPA method. Along with FR20RV, the following primers were used: lane 1, 1F; lane 2, 2F; lane 3, 3F; lane 4, 4R; lane 5, 5R; lane 6, 6R; lane 7, negative control; and lane M, DNA markers.
Fig. 5.
Fig. 5.
Circular genome map of ACV. The ORFs are marked with arrows indicating the direction of transcription. The ORFs encoding putative proteins for which functions could be predicted are color-coded as follows: thioredoxins, yellow; carbohydrate metabolism, green; DNA binding, blue; serine protease, gray; and recombinase, red.
Fig. 6.
Fig. 6.
Schematic representation of different levels of organization of the circular ACV nucleoprotein. As described in the text, the two halves of the circular nucleoprotein (A) intertwine with each other and form a nucleoprotein filament (B), which is condensed into the helical coil of the virion (C).

Similar articles

See all similar articles

Cited by 31 articles

See all "Cited by" articles

Publication types

MeSH terms

Associated data

LinkOut - more resources

Feedback