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A genetic study of SSV1, the prototypical fusellovirus.

Iverson E, Stedman K - Front Microbiol (2012)

Bottom Line: Recently we have developed genetic tools to analyze these genes.In this study, we have deleted three SSV1 open reading frames (ORFs) ranging from completely conserved to poorly conserved: VP2, d244, and b129.Deletion of the universally conserved ORF b129, which encodes a predicted transcriptional regulator, results in loss of infectivity.

View Article: PubMed Central - PubMed

Affiliation: Biology Department, Center for Life in Extreme Environments, Portland State University, Portland, OR, USA.

ABSTRACT
Viruses of thermophilic Archaea are unique in both their structures and genomic sequences. The most widespread and arguably best studied are the lemon-shaped fuselloviruses. The spindle-shaped virus morphology is unique to Archaea but widespread therein. The best studied fusellovirus is SSV1 from Beppu, Japan, which infects Sulfolobus solfataricus. Very little is known about the function of the genes in the SSV1 genome. Recently we have developed genetic tools to analyze these genes. In this study, we have deleted three SSV1 open reading frames (ORFs) ranging from completely conserved to poorly conserved: VP2, d244, and b129. Deletion of the universally conserved ORF b129, which encodes a predicted transcriptional regulator, results in loss of infectivity. Deletion of the poorly conserved predicted DNA-binding protein gene VP2 yields viable virus that is indistinguishable from wild-type. Deletion of the well-conserved ORF d244 that encodes a predicted nuclease yields viable virus. However, infection of S. solfataricus with virus lacking ORF d244 dramatically retards host growth, compared to the wild-type virus.

No MeSH data available.


Related in: MedlinePlus

Genome map of SSV1. Open reading frames are shown as block arrows and labeled as in Palm et al. (1991). Virus structural protein genes (Reiter et al., 1987a) and other proteins found in the virion (Menon et al., 2008) are outlined in red and labeled as “in virion.” Conservation of open reading frames in 12 canonical SSV genomes (SSV1, SSV2, SSV3, SSV4, SSV5, SSVRH, SSVK1, SSVL, SSVKM1, SSVKU1, SSVL2, and SSVGV1; Redder et al., 2009; Held and Whitaker, 2009; Stedman, unpublished) is listed with the color code in the middle of the genome with ORFs conserved in 12 genomes in black, ORFs conserved in 11 genomes in dark blue, etc. ORFs which did not tolerate insertion of the pBluescript plasmid are labeled as “Essential” in blue type. ORFs allowing insertion of the pBluescript plasmid without loss of virus function are labeled as “not essential” (Stedman et al., 1999). All ORFs whose products have been crystallized and structure determined are labeled as “Structure” (Lawrence et al., 2009; Menon et al., 2010). The gene for the SSV1-integrase is labeled in green and was shown to be not essential by deletion (Clore and Stedman, 2006). Transcripts are labeled as curved thin arrows (Reiter et al., 1987b; Fröls et al., 2007). ORFs targeted in this study are indicated with large arrows outside the genome map.
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Figure 1: Genome map of SSV1. Open reading frames are shown as block arrows and labeled as in Palm et al. (1991). Virus structural protein genes (Reiter et al., 1987a) and other proteins found in the virion (Menon et al., 2008) are outlined in red and labeled as “in virion.” Conservation of open reading frames in 12 canonical SSV genomes (SSV1, SSV2, SSV3, SSV4, SSV5, SSVRH, SSVK1, SSVL, SSVKM1, SSVKU1, SSVL2, and SSVGV1; Redder et al., 2009; Held and Whitaker, 2009; Stedman, unpublished) is listed with the color code in the middle of the genome with ORFs conserved in 12 genomes in black, ORFs conserved in 11 genomes in dark blue, etc. ORFs which did not tolerate insertion of the pBluescript plasmid are labeled as “Essential” in blue type. ORFs allowing insertion of the pBluescript plasmid without loss of virus function are labeled as “not essential” (Stedman et al., 1999). All ORFs whose products have been crystallized and structure determined are labeled as “Structure” (Lawrence et al., 2009; Menon et al., 2010). The gene for the SSV1-integrase is labeled in green and was shown to be not essential by deletion (Clore and Stedman, 2006). Transcripts are labeled as curved thin arrows (Reiter et al., 1987b; Fröls et al., 2007). ORFs targeted in this study are indicated with large arrows outside the genome map.

Mentions: The Sulfolobus spindle-shaped viruses (SSVs) of the family Fuselloviridae were the first discovered and probably the best studied family of archaeal viruses. SSVs are found throughout the world in high temperature (> 70°C) and acidic (pH < 4) environments where their hosts, Sulfolobus solfataricus and its close relatives thrive (Wiedenheft et al., 2004; Held and Whitaker, 2009). The type virus, SSV1, encodes a positively supercoiled, 15.5 kbp circular dsDNA genome (NC_001338.1) that is enclosed within a lemon or spindle-shaped capsid (Yeats et al., 1982; Martin et al., 1984; Nadal et al., 1986). The genome encodes 34 open reading frames (ORFs; Palm et al., 1991), most of which have no recognizable homologs apart from other Fuselloviridae. The only SSV1 gene with clear homology to proteins outside the Fuselloviridae is the viral integrase, encoded by ORF d355. The main structural proteins purified from virus particles are the major and minor capsid proteins VP1 and VP3 and the putative DNA packaging protein VP2 (Reiter et al., 1987a). More recently, mass spectrometric analysis of SSV1 virions revealed two additional proteins, the products of ORFs c792 and d244 (Menon et al., 2008; Figure 1).


A genetic study of SSV1, the prototypical fusellovirus.

Iverson E, Stedman K - Front Microbiol (2012)

Genome map of SSV1. Open reading frames are shown as block arrows and labeled as in Palm et al. (1991). Virus structural protein genes (Reiter et al., 1987a) and other proteins found in the virion (Menon et al., 2008) are outlined in red and labeled as “in virion.” Conservation of open reading frames in 12 canonical SSV genomes (SSV1, SSV2, SSV3, SSV4, SSV5, SSVRH, SSVK1, SSVL, SSVKM1, SSVKU1, SSVL2, and SSVGV1; Redder et al., 2009; Held and Whitaker, 2009; Stedman, unpublished) is listed with the color code in the middle of the genome with ORFs conserved in 12 genomes in black, ORFs conserved in 11 genomes in dark blue, etc. ORFs which did not tolerate insertion of the pBluescript plasmid are labeled as “Essential” in blue type. ORFs allowing insertion of the pBluescript plasmid without loss of virus function are labeled as “not essential” (Stedman et al., 1999). All ORFs whose products have been crystallized and structure determined are labeled as “Structure” (Lawrence et al., 2009; Menon et al., 2010). The gene for the SSV1-integrase is labeled in green and was shown to be not essential by deletion (Clore and Stedman, 2006). Transcripts are labeled as curved thin arrows (Reiter et al., 1987b; Fröls et al., 2007). ORFs targeted in this study are indicated with large arrows outside the genome map.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3367457&req=5

Figure 1: Genome map of SSV1. Open reading frames are shown as block arrows and labeled as in Palm et al. (1991). Virus structural protein genes (Reiter et al., 1987a) and other proteins found in the virion (Menon et al., 2008) are outlined in red and labeled as “in virion.” Conservation of open reading frames in 12 canonical SSV genomes (SSV1, SSV2, SSV3, SSV4, SSV5, SSVRH, SSVK1, SSVL, SSVKM1, SSVKU1, SSVL2, and SSVGV1; Redder et al., 2009; Held and Whitaker, 2009; Stedman, unpublished) is listed with the color code in the middle of the genome with ORFs conserved in 12 genomes in black, ORFs conserved in 11 genomes in dark blue, etc. ORFs which did not tolerate insertion of the pBluescript plasmid are labeled as “Essential” in blue type. ORFs allowing insertion of the pBluescript plasmid without loss of virus function are labeled as “not essential” (Stedman et al., 1999). All ORFs whose products have been crystallized and structure determined are labeled as “Structure” (Lawrence et al., 2009; Menon et al., 2010). The gene for the SSV1-integrase is labeled in green and was shown to be not essential by deletion (Clore and Stedman, 2006). Transcripts are labeled as curved thin arrows (Reiter et al., 1987b; Fröls et al., 2007). ORFs targeted in this study are indicated with large arrows outside the genome map.
Mentions: The Sulfolobus spindle-shaped viruses (SSVs) of the family Fuselloviridae were the first discovered and probably the best studied family of archaeal viruses. SSVs are found throughout the world in high temperature (> 70°C) and acidic (pH < 4) environments where their hosts, Sulfolobus solfataricus and its close relatives thrive (Wiedenheft et al., 2004; Held and Whitaker, 2009). The type virus, SSV1, encodes a positively supercoiled, 15.5 kbp circular dsDNA genome (NC_001338.1) that is enclosed within a lemon or spindle-shaped capsid (Yeats et al., 1982; Martin et al., 1984; Nadal et al., 1986). The genome encodes 34 open reading frames (ORFs; Palm et al., 1991), most of which have no recognizable homologs apart from other Fuselloviridae. The only SSV1 gene with clear homology to proteins outside the Fuselloviridae is the viral integrase, encoded by ORF d355. The main structural proteins purified from virus particles are the major and minor capsid proteins VP1 and VP3 and the putative DNA packaging protein VP2 (Reiter et al., 1987a). More recently, mass spectrometric analysis of SSV1 virions revealed two additional proteins, the products of ORFs c792 and d244 (Menon et al., 2008; Figure 1).

Bottom Line: Recently we have developed genetic tools to analyze these genes.In this study, we have deleted three SSV1 open reading frames (ORFs) ranging from completely conserved to poorly conserved: VP2, d244, and b129.Deletion of the universally conserved ORF b129, which encodes a predicted transcriptional regulator, results in loss of infectivity.

View Article: PubMed Central - PubMed

Affiliation: Biology Department, Center for Life in Extreme Environments, Portland State University, Portland, OR, USA.

ABSTRACT
Viruses of thermophilic Archaea are unique in both their structures and genomic sequences. The most widespread and arguably best studied are the lemon-shaped fuselloviruses. The spindle-shaped virus morphology is unique to Archaea but widespread therein. The best studied fusellovirus is SSV1 from Beppu, Japan, which infects Sulfolobus solfataricus. Very little is known about the function of the genes in the SSV1 genome. Recently we have developed genetic tools to analyze these genes. In this study, we have deleted three SSV1 open reading frames (ORFs) ranging from completely conserved to poorly conserved: VP2, d244, and b129. Deletion of the universally conserved ORF b129, which encodes a predicted transcriptional regulator, results in loss of infectivity. Deletion of the poorly conserved predicted DNA-binding protein gene VP2 yields viable virus that is indistinguishable from wild-type. Deletion of the well-conserved ORF d244 that encodes a predicted nuclease yields viable virus. However, infection of S. solfataricus with virus lacking ORF d244 dramatically retards host growth, compared to the wild-type virus.

No MeSH data available.


Related in: MedlinePlus