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A unique spumavirus Gag N-terminal domain with functional properties of orthoretroviral matrix and capsid.

Goldstone DC, Flower TG, Ball NJ, Sanz-Ramos M, Yap MW, Ogrodowicz RW, Stanke N, Reh J, Lindemann D, Stoye JP, Taylor IA - PLoS Pathog. (2013)

Bottom Line: Although FV infection is apparently benign, trans-species zoonosis is commonplace and has resulted in the isolation of the Prototypic Foamy Virus (PFV) from human sources and the potential for germ-line transmission.Furthermore, we present structural, biochemical and virological data that reveal the molecular details of the essential Gag-Env interaction and in addition we also examine the specificity of Trim5α restriction of PFV.These data provide the first information with regards to FV structural proteins and suggest a model for convergent evolution of gag genes where structurally unrelated molecules have become functionally equivalent.

View Article: PubMed Central - PubMed

Affiliation: Division of Molecular Structure, MRC National Institute for Medical Research, the Ridgeway, Mill Hill, London, United Kingdom.

ABSTRACT
The Spumaretrovirinae, or foamyviruses (FVs) are complex retroviruses that infect many species of monkey and ape. Although FV infection is apparently benign, trans-species zoonosis is commonplace and has resulted in the isolation of the Prototypic Foamy Virus (PFV) from human sources and the potential for germ-line transmission. Despite little sequence homology, FV and orthoretroviral Gag proteins perform equivalent functions, including genome packaging, virion assembly, trafficking and membrane targeting. In addition, PFV Gag interacts with the FV Envelope (Env) protein to facilitate budding of infectious particles. Presently, there is a paucity of structural information with regards FVs and it is unclear how disparate FV and orthoretroviral Gag molecules share the same function. Therefore, in order to probe the functional overlap of FV and orthoretroviral Gag and learn more about FV egress and replication we have undertaken a structural, biophysical and virological study of PFV-Gag. We present the crystal structure of a dimeric amino terminal domain from PFV, Gag-NtD, both free and in complex with the leader peptide of PFV Env. The structure comprises a head domain together with a coiled coil that forms the dimer interface and despite the shared function it is entirely unrelated to either the capsid or matrix of Gag from other retroviruses. Furthermore, we present structural, biochemical and virological data that reveal the molecular details of the essential Gag-Env interaction and in addition we also examine the specificity of Trim5α restriction of PFV. These data provide the first information with regards to FV structural proteins and suggest a model for convergent evolution of gag genes where structurally unrelated molecules have become functionally equivalent.

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Restriction of foamy viruses.(A) Schematic bar representations of Gag from PFV (blue) and SFVmac (red) along with chimeric PSG-4 (amino acids 1–311 PFV + 302–647 SFV), SPG-4 (amino acids 1–301 SFV + 312–648 PFV), PSG-5 (amino acids 1–195 PFV + 187–647 SFV) and SPG-5 (amino acids 1–186 SFV + 196–648 PFV) are shown on the left with C-terminal Gag P3 peptide coloured green and coiled coil regions hatched. Restriction of each virus by Brown Capuchin Trim5α is shown on the right. The values are the average from three independent experiments detailed in full in Supplementary Figure S3. (B) Mapping of the interfacial, conserved and non-conserved residues onto the PFV structure. The structure of PFV -Gag-Ntd is shown as a semi transparent surface surrounding a cartoon ribbon representation of the protein backbone. Residues that contribute to the dimer interface are shown in orange. Residues that are sequence conserved in SFVmac and PFV are displayed in cyan and residues that are surface-exposed and non-conserved are displayed in blue.
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ppat-1003376-g007: Restriction of foamy viruses.(A) Schematic bar representations of Gag from PFV (blue) and SFVmac (red) along with chimeric PSG-4 (amino acids 1–311 PFV + 302–647 SFV), SPG-4 (amino acids 1–301 SFV + 312–648 PFV), PSG-5 (amino acids 1–195 PFV + 187–647 SFV) and SPG-5 (amino acids 1–186 SFV + 196–648 PFV) are shown on the left with C-terminal Gag P3 peptide coloured green and coiled coil regions hatched. Restriction of each virus by Brown Capuchin Trim5α is shown on the right. The values are the average from three independent experiments detailed in full in Supplementary Figure S3. (B) Mapping of the interfacial, conserved and non-conserved residues onto the PFV structure. The structure of PFV -Gag-Ntd is shown as a semi transparent surface surrounding a cartoon ribbon representation of the protein backbone. Residues that contribute to the dimer interface are shown in orange. Residues that are sequence conserved in SFVmac and PFV are displayed in cyan and residues that are surface-exposed and non-conserved are displayed in blue.

Mentions: Previous experiments have demonstrated that Gag from PFV and the closely related SFVmac contain the target for Trim5α restriction. Moreover, PFV and SFVmac display a differential susceptibility to restriction mediated by the B30.2 domain of Brown capuchin Trim5α (bc-T5α) that is effective only against SFVmac and not PFV [36]. Based on sequence alignment, chimeras were prepared to more precisely map the target of Trim5α restriction in FV Gag. These included PSG-4 and SPG-4, that swap the N-terminal ∼300 residues between PFV and SFVmac Gag and two further chimeras, one where the N-terminal 186 residues of SFVmac Gag was replaced by the N-terminal 195 residues of PFV Gag (PSG-5) and a second where the N-terminal 195 residues of PFV Gag was replaced with the N-terminal 186 residues of SFVmac Gag (SPG-5). The results of bc-T5α restriction assays of parent and chimeric PFV and SFVmac viruses are summarised in Figure 7A, and detailed in Supplementary Figure S3. These data confirm that PFV is resistant to bc-T5α restriction and that SFVmac is susceptible, and that sensitivity maps the N-terminal 300 amino acids of Gag, Figure 7A (PSG-4 and SPG-4). More importantly, these data also reveal that transfer of the N-terminal 186 residues of SFVmac to PFV (SPG-5) now renders the virus susceptible to restriction by bc-T5α. Conversely, transfer of N-terminal 195 residues of PFV to SFVmac (PSG-5) results in reduced sensitivity to bc-T5α restriction demonstrating that at least one determinant of restriction in primate FVs is contained within the Gag-NtD.


A unique spumavirus Gag N-terminal domain with functional properties of orthoretroviral matrix and capsid.

Goldstone DC, Flower TG, Ball NJ, Sanz-Ramos M, Yap MW, Ogrodowicz RW, Stanke N, Reh J, Lindemann D, Stoye JP, Taylor IA - PLoS Pathog. (2013)

Restriction of foamy viruses.(A) Schematic bar representations of Gag from PFV (blue) and SFVmac (red) along with chimeric PSG-4 (amino acids 1–311 PFV + 302–647 SFV), SPG-4 (amino acids 1–301 SFV + 312–648 PFV), PSG-5 (amino acids 1–195 PFV + 187–647 SFV) and SPG-5 (amino acids 1–186 SFV + 196–648 PFV) are shown on the left with C-terminal Gag P3 peptide coloured green and coiled coil regions hatched. Restriction of each virus by Brown Capuchin Trim5α is shown on the right. The values are the average from three independent experiments detailed in full in Supplementary Figure S3. (B) Mapping of the interfacial, conserved and non-conserved residues onto the PFV structure. The structure of PFV -Gag-Ntd is shown as a semi transparent surface surrounding a cartoon ribbon representation of the protein backbone. Residues that contribute to the dimer interface are shown in orange. Residues that are sequence conserved in SFVmac and PFV are displayed in cyan and residues that are surface-exposed and non-conserved are displayed in blue.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3649970&req=5

ppat-1003376-g007: Restriction of foamy viruses.(A) Schematic bar representations of Gag from PFV (blue) and SFVmac (red) along with chimeric PSG-4 (amino acids 1–311 PFV + 302–647 SFV), SPG-4 (amino acids 1–301 SFV + 312–648 PFV), PSG-5 (amino acids 1–195 PFV + 187–647 SFV) and SPG-5 (amino acids 1–186 SFV + 196–648 PFV) are shown on the left with C-terminal Gag P3 peptide coloured green and coiled coil regions hatched. Restriction of each virus by Brown Capuchin Trim5α is shown on the right. The values are the average from three independent experiments detailed in full in Supplementary Figure S3. (B) Mapping of the interfacial, conserved and non-conserved residues onto the PFV structure. The structure of PFV -Gag-Ntd is shown as a semi transparent surface surrounding a cartoon ribbon representation of the protein backbone. Residues that contribute to the dimer interface are shown in orange. Residues that are sequence conserved in SFVmac and PFV are displayed in cyan and residues that are surface-exposed and non-conserved are displayed in blue.
Mentions: Previous experiments have demonstrated that Gag from PFV and the closely related SFVmac contain the target for Trim5α restriction. Moreover, PFV and SFVmac display a differential susceptibility to restriction mediated by the B30.2 domain of Brown capuchin Trim5α (bc-T5α) that is effective only against SFVmac and not PFV [36]. Based on sequence alignment, chimeras were prepared to more precisely map the target of Trim5α restriction in FV Gag. These included PSG-4 and SPG-4, that swap the N-terminal ∼300 residues between PFV and SFVmac Gag and two further chimeras, one where the N-terminal 186 residues of SFVmac Gag was replaced by the N-terminal 195 residues of PFV Gag (PSG-5) and a second where the N-terminal 195 residues of PFV Gag was replaced with the N-terminal 186 residues of SFVmac Gag (SPG-5). The results of bc-T5α restriction assays of parent and chimeric PFV and SFVmac viruses are summarised in Figure 7A, and detailed in Supplementary Figure S3. These data confirm that PFV is resistant to bc-T5α restriction and that SFVmac is susceptible, and that sensitivity maps the N-terminal 300 amino acids of Gag, Figure 7A (PSG-4 and SPG-4). More importantly, these data also reveal that transfer of the N-terminal 186 residues of SFVmac to PFV (SPG-5) now renders the virus susceptible to restriction by bc-T5α. Conversely, transfer of N-terminal 195 residues of PFV to SFVmac (PSG-5) results in reduced sensitivity to bc-T5α restriction demonstrating that at least one determinant of restriction in primate FVs is contained within the Gag-NtD.

Bottom Line: Although FV infection is apparently benign, trans-species zoonosis is commonplace and has resulted in the isolation of the Prototypic Foamy Virus (PFV) from human sources and the potential for germ-line transmission.Furthermore, we present structural, biochemical and virological data that reveal the molecular details of the essential Gag-Env interaction and in addition we also examine the specificity of Trim5α restriction of PFV.These data provide the first information with regards to FV structural proteins and suggest a model for convergent evolution of gag genes where structurally unrelated molecules have become functionally equivalent.

View Article: PubMed Central - PubMed

Affiliation: Division of Molecular Structure, MRC National Institute for Medical Research, the Ridgeway, Mill Hill, London, United Kingdom.

ABSTRACT
The Spumaretrovirinae, or foamyviruses (FVs) are complex retroviruses that infect many species of monkey and ape. Although FV infection is apparently benign, trans-species zoonosis is commonplace and has resulted in the isolation of the Prototypic Foamy Virus (PFV) from human sources and the potential for germ-line transmission. Despite little sequence homology, FV and orthoretroviral Gag proteins perform equivalent functions, including genome packaging, virion assembly, trafficking and membrane targeting. In addition, PFV Gag interacts with the FV Envelope (Env) protein to facilitate budding of infectious particles. Presently, there is a paucity of structural information with regards FVs and it is unclear how disparate FV and orthoretroviral Gag molecules share the same function. Therefore, in order to probe the functional overlap of FV and orthoretroviral Gag and learn more about FV egress and replication we have undertaken a structural, biophysical and virological study of PFV-Gag. We present the crystal structure of a dimeric amino terminal domain from PFV, Gag-NtD, both free and in complex with the leader peptide of PFV Env. The structure comprises a head domain together with a coiled coil that forms the dimer interface and despite the shared function it is entirely unrelated to either the capsid or matrix of Gag from other retroviruses. Furthermore, we present structural, biochemical and virological data that reveal the molecular details of the essential Gag-Env interaction and in addition we also examine the specificity of Trim5α restriction of PFV. These data provide the first information with regards to FV structural proteins and suggest a model for convergent evolution of gag genes where structurally unrelated molecules have become functionally equivalent.

Show MeSH
Related in: MedlinePlus