PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-6 (6)
 

Clipboard (0)
None
Journals
Authors
more »
Year of Publication
Document Types
4.  The GLN Family of Murine Endogenous Retroviruses Contains an Element Competent for Infectious Viral Particle Formation▿  
Journal of Virology  2008;82(9):4413-4419.
Several families of endogenous retroviruses (ERVs) have been identified in the mouse genome, in several instances by in silico searches, but for many of them it remains to be determined whether there are elements that can still encode functional retroviral particles. Here, we identify, within the GLN family of highly reiterated ERVs, one, and only one, copy that encodes retroviral particles prone to infection of mouse cells. We show that its envelope protein confers an ecotropic host range and recognizes a receptor different from mCAT1 and mSMIT1, the two previously identified receptors for other ecotropic mouse retroviruses. Electron microscopy disclosed viral particle assembly and budding at the cell membrane, as well as release of mature particles into the extracellular space. These particles are closely related to murine leukemia virus (MLV) particles, with which they have most probably been confused in the past. This study, therefore, identifies a new class of infectious mouse ERVs belonging to the family Gammaretroviridae, with one family member still functional today. This family is in addition to the two MLV and mouse mammary tumor virus families of active mouse ERVs with an extracellular life cycle.
doi:10.1128/JVI.02141-07
PMCID: PMC2293071  PMID: 18287236
5.  Murine Endogenous Retrovirus MuERV-L Is the Progenitor of the “Orphan” Epsilon Viruslike Particles of the Early Mouse Embryo▿  
Journal of Virology  2007;82(3):1622-1625.
Viruslike particles which displayed a peculiar wheellike appearance that distinguished them from A-, B- or C-type particles had previously been described in the early mouse embryo. The maximum expression of these so-called epsilon particles was observed in two-cell-stage embryos, followed by their rapid decline at later stages of development and no particles detected at the zygote one-cell stage. Here, we show that these particles are in fact produced by a newly discovered murine endogenous retrovirus (ERV) belonging to the widespread family of mammalian ERV-L elements and named MuERV-L. Using antibodies that we raised against the Gag protein of these elements, Western blot analysis and in toto immunofluorescence studies of the embryos at various stages disclosed the same developmental expression profile as that observed for epsilon particles. Using expression vectors for cloned, full-length, entirely coding MuERV-L copies and cell transfection, direct identification of the epsilon particles was finally achieved by high-resolution electron microscopy.
doi:10.1128/JVI.02097-07
PMCID: PMC2224431  PMID: 18045933
6.  Murine MusD Retrotransposon: Structure and Molecular Evolution of an “Intracellularized” Retrovirus▿  
Journal of Virology  2006;81(4):1888-1898.
We had previously identified active autonomous copies of the MusD long terminal repeat-retrotransposon family, which have retained transpositional activity. These elements are closely related to betaretroviruses but lack an envelope (env) gene. Here we show that these elements encode strictly intracellular virus-like particles that can unambiguously be identified by electron microscopy. We demonstrate intracellular maturation of the particles, with a significant proportion of densely packed cores for wild-type MusD but not for a protease mutant. We show that the molecular origin of this unexpected intracellular localization is solely dependent on the N-terminal part of the Gag protein, which lacks a functional sequence for myristoylation and plasma membrane targeting: replacement of the N-terminal domain of the MusD matrix protein by that of its closest relative—the Mason-Pfizer monkey virus—led to targeting of the MusD Gag to the plasma membrane, with viral particles budding and being released into the cell supernatant. These particles can further be pseudotyped with a heterologous envelope protein and become infectious, thus “reconstituting” a functional retrovirus prone to proviral insertions. Consistent with its retroviral origin, a sequence with a constitutive transport element-like activity can further be identified at the MusD 3′ untranslated region. A molecular scenario is proposed that accounts for the transition, during evolution, from an ancestral infectious betaretrovirus to the strictly intracellular MusD retrotransposon, involving not only the loss of the env gene but also an inability to escape the cell—via altered targeting of the Gag protein—resulting de facto in the generation of a very successful “intracellularized” insertional mutagen.
doi:10.1128/JVI.02051-06
PMCID: PMC1797557  PMID: 17151128

Results 1-6 (6)