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Impairment of alternative splice sites defining a novel gammaretroviral exon within gag modifies the oncogenic properties of Akv murine leukemia virus.

Sørensen AB, Lund AH, Kunder S, Quintanilla-Martinez L, Schmidt J, Wang B, Wabl M, Pedersen FS - Retrovirology (2007)

Bottom Line: Interestingly, a broader spectrum of diagnoses was made from the two single splice-site mutants than from as well the wild-type as the double splice-site mutant.Both single- and double-spliced transcripts are produced in vivo using the SA' and/or the SD' sites, but the mechanisms underlying the observed effects on oncogenesis remain to be clarified.Likewise, analyses of provirus integration sites in tumor tissues, which identified 111 novel RISs (retroviral integration sites) and 35 novel CISs (common integration sites), did not clearly point to specific target genes or pathways to be associated with specific tumor diagnoses or individual viral mutants.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Molecular Biology, University of Aarhus, Denmark. abs@statsbiblioteket.dk

ABSTRACT

Background: Mutations of an alternative splice donor site located within the gag region has previously been shown to broaden the pathogenic potential of the T-lymphomagenic gammaretrovirus Moloney murine leukemia virus, while the equivalent mutations in the erythroleukemia inducing Friend murine leukemia virus seem to have no influence on the disease-inducing potential of this virus. In the present study we investigate the splice pattern as well as the possible effects of mutating the alternative splice sites on the oncogenic properties of the B-lymphomagenic Akv murine leukemia virus.

Results: By exon-trapping procedures we have identified a novel gammaretroviral exon, resulting from usage of alternative splice acceptor (SA') and splice donor (SD') sites located in the capsid region of gag of the B-cell lymphomagenic Akv murine leukemia virus. To analyze possible effects in vivo of this novel exon, three different alternative splice site mutant viruses, mutated in either the SA', in the SD', or in both sites, respectively, were constructed and injected into newborn inbred NMRI mice. Most of the infected mice (about 90%) developed hematopoietic neoplasms within 250 days, and histological examination of the tumors showed that the introduced synonymous gag mutations have a significant influence on the phenotype of the induced tumors, changing the distribution of the different types as well as generating tumors of additional specificities such as de novo diffuse large B cell lymphoma (DLBCL) and histiocytic sarcoma. Interestingly, a broader spectrum of diagnoses was made from the two single splice-site mutants than from as well the wild-type as the double splice-site mutant. Both single- and double-spliced transcripts are produced in vivo using the SA' and/or the SD' sites, but the mechanisms underlying the observed effects on oncogenesis remain to be clarified. Likewise, analyses of provirus integration sites in tumor tissues, which identified 111 novel RISs (retroviral integration sites) and 35 novel CISs (common integration sites), did not clearly point to specific target genes or pathways to be associated with specific tumor diagnoses or individual viral mutants.

Conclusion: We present here the first example of a doubly spliced transcript within the group of gammaretroviruses, and we show that mutation of the alternative splice sites that define this novel RNA product change the oncogenic potential of Akv murine leukemia virus.

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DNA sequence alignment around the Akv MLV SA' site in the capsid-coding region of a series of different ecotropic MLVs. The 3' splice acceptor site consensus sequences are shown on top, with the border of the novel gag exon indicated by a vertical line. The boldfaced A in the sequence indicates the presumed branch point.
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Figure 6: DNA sequence alignment around the Akv MLV SA' site in the capsid-coding region of a series of different ecotropic MLVs. The 3' splice acceptor site consensus sequences are shown on top, with the border of the novel gag exon indicated by a vertical line. The boldfaced A in the sequence indicates the presumed branch point.

Mentions: We have in the B-lymphomagenic Akv MLV identified a novel exon, which is defined by the alternative splice acceptor (SA') and the splice donor (SD') sites located in the capsid encoding region. While previous studies of Moloney and Friend MLV have demonstrated production of a 4.4 kb transcript using the same SD' site together with the canonical env SA site, this is the first report demonstrating the existence of an alternative SA' site and production of a double-spliced transcript during the life cycle of a replication-competent simple retrovirus. Yet it remains to be investigated how widespread this competence is. An alignment between six murine retroviruses shows that the conserved splice junction dinucleotide AG is present neither in Cas-Br-E nor in Moloney MLV, although the region in general is well-conserved (Fig. 6).


Impairment of alternative splice sites defining a novel gammaretroviral exon within gag modifies the oncogenic properties of Akv murine leukemia virus.

Sørensen AB, Lund AH, Kunder S, Quintanilla-Martinez L, Schmidt J, Wang B, Wabl M, Pedersen FS - Retrovirology (2007)

DNA sequence alignment around the Akv MLV SA' site in the capsid-coding region of a series of different ecotropic MLVs. The 3' splice acceptor site consensus sequences are shown on top, with the border of the novel gag exon indicated by a vertical line. The boldfaced A in the sequence indicates the presumed branch point.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1936429&req=5

Figure 6: DNA sequence alignment around the Akv MLV SA' site in the capsid-coding region of a series of different ecotropic MLVs. The 3' splice acceptor site consensus sequences are shown on top, with the border of the novel gag exon indicated by a vertical line. The boldfaced A in the sequence indicates the presumed branch point.
Mentions: We have in the B-lymphomagenic Akv MLV identified a novel exon, which is defined by the alternative splice acceptor (SA') and the splice donor (SD') sites located in the capsid encoding region. While previous studies of Moloney and Friend MLV have demonstrated production of a 4.4 kb transcript using the same SD' site together with the canonical env SA site, this is the first report demonstrating the existence of an alternative SA' site and production of a double-spliced transcript during the life cycle of a replication-competent simple retrovirus. Yet it remains to be investigated how widespread this competence is. An alignment between six murine retroviruses shows that the conserved splice junction dinucleotide AG is present neither in Cas-Br-E nor in Moloney MLV, although the region in general is well-conserved (Fig. 6).

Bottom Line: Interestingly, a broader spectrum of diagnoses was made from the two single splice-site mutants than from as well the wild-type as the double splice-site mutant.Both single- and double-spliced transcripts are produced in vivo using the SA' and/or the SD' sites, but the mechanisms underlying the observed effects on oncogenesis remain to be clarified.Likewise, analyses of provirus integration sites in tumor tissues, which identified 111 novel RISs (retroviral integration sites) and 35 novel CISs (common integration sites), did not clearly point to specific target genes or pathways to be associated with specific tumor diagnoses or individual viral mutants.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Molecular Biology, University of Aarhus, Denmark. abs@statsbiblioteket.dk

ABSTRACT

Background: Mutations of an alternative splice donor site located within the gag region has previously been shown to broaden the pathogenic potential of the T-lymphomagenic gammaretrovirus Moloney murine leukemia virus, while the equivalent mutations in the erythroleukemia inducing Friend murine leukemia virus seem to have no influence on the disease-inducing potential of this virus. In the present study we investigate the splice pattern as well as the possible effects of mutating the alternative splice sites on the oncogenic properties of the B-lymphomagenic Akv murine leukemia virus.

Results: By exon-trapping procedures we have identified a novel gammaretroviral exon, resulting from usage of alternative splice acceptor (SA') and splice donor (SD') sites located in the capsid region of gag of the B-cell lymphomagenic Akv murine leukemia virus. To analyze possible effects in vivo of this novel exon, three different alternative splice site mutant viruses, mutated in either the SA', in the SD', or in both sites, respectively, were constructed and injected into newborn inbred NMRI mice. Most of the infected mice (about 90%) developed hematopoietic neoplasms within 250 days, and histological examination of the tumors showed that the introduced synonymous gag mutations have a significant influence on the phenotype of the induced tumors, changing the distribution of the different types as well as generating tumors of additional specificities such as de novo diffuse large B cell lymphoma (DLBCL) and histiocytic sarcoma. Interestingly, a broader spectrum of diagnoses was made from the two single splice-site mutants than from as well the wild-type as the double splice-site mutant. Both single- and double-spliced transcripts are produced in vivo using the SA' and/or the SD' sites, but the mechanisms underlying the observed effects on oncogenesis remain to be clarified. Likewise, analyses of provirus integration sites in tumor tissues, which identified 111 novel RISs (retroviral integration sites) and 35 novel CISs (common integration sites), did not clearly point to specific target genes or pathways to be associated with specific tumor diagnoses or individual viral mutants.

Conclusion: We present here the first example of a doubly spliced transcript within the group of gammaretroviruses, and we show that mutation of the alternative splice sites that define this novel RNA product change the oncogenic potential of Akv murine leukemia virus.

Show MeSH
Related in: MedlinePlus