• MeSH
• Retroviridae MeSH
• retrovirové infekce diagnóza   etiologie   MeSH
• Publikační typ
• kongresy MeSH

The assembly of a hexameric lattice of retroviral immature particles requires the involvement of cell factors such as proteins and small molecules. A small, negatively charged polyanionic molecule, myo-inositol hexaphosphate (IP6), was identified to stimulate the assembly of immature particles of HIV-1 and other lentiviruses. Interestingly, cryo-electron tomography analysis of the immature particles of two lentiviruses, HIV-1 and equine infectious anemia virus (EIAV), revealed that the IP6 binding site is similar. Based on this amino acid conservation of the IP6 interacting site, it is presumed that the assembly of immature particles of all lentiviruses is stimulated by IP6. Although this specific region for IP6 binding may be unique for lentiviruses, it is plausible that other retroviral species also recruit some small polyanion to facilitate the assembly of their immature particles. To study whether the assembly of retroviruses other than lentiviruses can be stimulated by polyanionic molecules, we measured the effect of various polyanions on the assembly of immature virus-like particles of Rous sarcoma virus (RSV), a member of alpharetroviruses, Mason-Pfizer monkey virus (M-PMV) representative of betaretroviruses, and murine leukemia virus (MLV), a member of gammaretroviruses. RSV, M-PMV and MLV immature virus-like particles were assembled in vitro from truncated Gag molecules and the effect of selected polyanions, myo-inostol hexaphosphate, myo-inositol, glucose-1,6-bisphosphate, myo-inositol hexasulphate, and mellitic acid, on the particles assembly was quantified. Our results suggest that the assembly of immature particles of RSV and MLV was indeed stimulated by the presence of myo-inostol hexaphosphate and myo-inositol, respectively. In contrast, no effect on the assembly of M-PMV as a betaretrovirus member was observed.

• MeSH
• Alpharetrovirus fyziologie   MeSH
• Betaretrovirus fyziologie   MeSH
• buněčná membrána chemie   metabolismus   MeSH
• Gammaretrovirus fyziologie   MeSH
• genové produkty gag chemie   metabolismus   MeSH
• interakce hostitele a patogenu * MeSH
• kultivované buňky MeSH
• polyelektrolyty chemie   metabolismus   MeSH
• Retroviridae fyziologie   ultrastruktura   MeSH
• sestavení viru * MeSH
• virion MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

UNLABELLED: The hexameric lattice of an immature retroviral particle consists of Gag polyprotein, which is the precursor of all viral structural proteins. Lentiviral and alpharetroviral Gag proteins contain a peptide sequence called the spacer peptide (SP), which is localized between the capsid (CA) and nucleocapsid (NC) domains. SP plays a critical role in intermolecular interactions during the assembly of immature particles of several retroviruses. Published models of supramolecular structures of immature particles suggest that in lentiviruses and alpharetroviruses, SP adopts a rod-like six-helix bundle organization. In contrast, Mason-Pfizer monkey virus (M-PMV), a betaretrovirus that assembles in the cytoplasm, does not contain a distinct SP sequence, and the CA-NC connecting region is not organized into a clear rod-like structure. Nevertheless, the CA-NC junction comprises a sequence critical for assembly of immature M-PMV particles. In the present work, we characterized this region, called the SP-like domain, in detail. We provide biochemical data confirming the critical role of the M-PMV SP-like domain in immature particle assembly, release, processing, and infectivity. Circular dichroism spectroscopy revealed that, in contrast to the SP regions of other retroviruses, a short SP-like domain-derived peptide (SPLP) does not form a purely helical structure in aqueous or helix-promoting solution. Using 8-Å cryo-electron microscopy density maps of immature M-PMV particles, we prepared computational models of the SP-like domain and indicate the structural features required for M-PMV immature particle assembly. IMPORTANCE: Retroviruses such as HIV-1 are of great medical importance. Using Mason-Pfizer monkey virus (M-PMV) as a model retrovirus, we provide biochemical and structural data confirming the general relevance of a short segment of the structural polyprotein Gag for retrovirus assembly and infectivity. Although this segment is critical for assembly of immature particles of lentiviruses, alpharetroviruses, and betaretroviruses, the organization of this domain is strikingly different. A previously published electron microscopic structure of an immature M-PMV particle allowed us to model this important region into the electron density map. The data presented here help explain the different packing of the Gag segments of various retroviruses, such as HIV, Rous sarcoma virus (RSV), and M-PMV. Such knowledge contributes to understanding the importance of this region and its structural flexibility among retroviral species. The region might play a key role in Gag-Gag interactions, leading to different morphological pathways of immature particle assembly.

• MeSH
• cirkulární dichroismus MeSH
• elektronová kryomikroskopie MeSH
• konformace proteinů MeSH
• Masonův-Pfizerův opičí virus fyziologie   MeSH
• molekulární modely MeSH
• nukleokapsida - proteiny chemie   genetika   metabolismus   ultrastruktura   MeSH
• sestavení viru * MeSH
• uvolnění viru z buňky MeSH
• virové plášťové proteiny chemie   genetika   metabolismus   ultrastruktura   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

UNLABELLED: The Gag polyprotein of retroviruses drives immature virus assembly by forming hexameric protein lattices. The assembly is primarily mediated by protein-protein interactions between capsid (CA) domains and by interactions between nucleocapsid (NC) domains and RNA. Specific interactions between NC and the viral RNA are required for genome packaging. Previously reported cryoelectron microscopy analysis of immature Mason-Pfizer monkey virus (M-PMV) particles suggested that a basic region (residues RKK) in CA may serve as an additional binding site for nucleic acids. Here, we have introduced mutations into the RKK region in both bacterial and proviral M-PMV vectors and have assessed their impact on M-PMV assembly, structure, RNA binding, budding/release, nuclear trafficking, and infectivity using in vitro and in vivo systems. Our data indicate that the RKK region binds and structures nucleic acid that serves to promote virus particle assembly in the cytoplasm. Moreover, the RKK region appears to be important for recruitment of viral genomic RNA into Gag particles, and this function could be linked to changes in nuclear trafficking. Together these observations suggest that in M-PMV, direct interactions between CA and nucleic acid play important functions in the late stages of the viral life cycle. IMPORTANCE: Assembly of retrovirus particles is driven by the Gag polyprotein, which can self-assemble to form virus particles and interact with RNA to recruit the viral genome into the particles. Generally, the capsid domains of Gag contribute to essential protein-protein interactions during assembly, while the nucleocapsid domain interacts with RNA. The interactions between the nucleocapsid domain and RNA are important both for identifying the genome and for self-assembly of Gag molecules. Here, we show that a region of basic residues in the capsid protein of the betaretrovirus Mason-Pfizer monkey virus (M-PMV) contributes to interaction of Gag with nucleic acid. This interaction appears to provide a critical scaffolding function that promotes assembly of virus particles in the cytoplasm. It is also crucial for packaging the viral genome and thus for infectivity. These data indicate that, surprisingly, interactions between the capsid domain and RNA play an important role in the assembly of M-PMV.

• MeSH
• buněčné linie MeSH
• elektronová kryomikroskopie MeSH
• genom virový * MeSH
• genové produkty gag MeSH
• lidé MeSH
• Masonův-Pfizerův opičí virus fyziologie   ultrastruktura   MeSH
• mutace MeSH
• rekombinantní proteiny MeSH
• RNA virová metabolismus   MeSH
• sekvence aminokyselin MeSH
• sestavení viru * genetika   MeSH
• substituce aminokyselin MeSH
• transport proteinů MeSH
• vazba proteinů MeSH
• virové plášťové proteiny genetika   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

In contrast to other retroviruses, Mason-Pfizer monkey virus (M-PMV) assembles immature capsids in the cytoplasm. We have compared the ability of minimal assembly-competent domains from M-PMV and human immunodeficiency virus type 1 (HIV-1) to assemble in vitro into virus-like particles in the presence and absence of nucleic acids. A fusion protein comprised of the capsid and nucleocapsid domains of Gag (CANC) and its N-terminally modified mutant (DeltaProCANC) were used to mimic the assembly of the viral core and immature particles, respectively. In contrast to HIV-1, where CANC assembled efficiently into cylindrical structures, the same domains of M-PMV were assembly incompetent. The addition of RNA or oligonucleotides did not complement this defect. In contrast, the M-PMV DeltaProCANC molecule was able to assemble into spherical particles, while that of HIV-1 formed both spheres and cylinders. For M-PMV, the addition of purified RNA increased the efficiency with which DeltaProCANC formed spherical particles both in terms of the overall amount and the numbers of completed spheres. The amount of RNA incorporated was determined, and for both rRNA and MS2-RNA, quantities similar to that of genomic RNA were encapsidated. Oligonucleotides also stimulated assembly; however, they were incorporated into DeltaProCANC spherical particles in trace amounts that could not serve as a stoichiometric structural component for assembly. Thus, oligonucleotides may, through a transient interaction, induce conformational changes that facilitate assembly, while longer RNAs appear to facilitate the complete assembly of spherical particles.

• MeSH
• bezbuněčný systém MeSH
• financování organizované MeSH
• genom virový fyziologie   MeSH
• genové produkty gag genetika   metabolismus   MeSH
• HIV-1 fyziologie   izolace a purifikace   ultrastruktura   MeSH
• kapsida metabolismus   ultrastruktura   MeSH
• konformace proteinů MeSH
• lidé MeSH
• Masonův-Pfizerův opičí virus fyziologie   izolace a purifikace   MeSH
• mutace MeSH
• oligonukleotidy genetika   metabolismus   MeSH
• RNA ribozomální genetika   metabolismus   MeSH
• RNA virová genetika   metabolismus   ultrastruktura   MeSH
• sestavení viru fyziologie   MeSH
• terciární struktura proteinů účinky léků   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• srovnávací studie MeSH

In addition to specific RNA-binding zinc finger domains, the retroviral Gag polyprotein contains clusters of basic amino acid residues that are thought to support Gag-viral genomic RNA (gRNA) interactions. One of these clusters is the basic K16NK18EK20 region, located upstream of the first zinc finger of the Mason-Pfizer monkey virus (M-PMV) nucleocapsid (NC) protein. To investigate the role of this basic region in the M-PMV life cycle, we used a combination of in vivo and in vitro methods to study a series of mutants in which the overall charge of this region was more positive (RNRER), more negative (AEAEA), or neutral (AAAAA). The mutations markedly affected gRNA incorporation and the onset of reverse transcription. The introduction of a more negative charge (AEAEA) significantly reduced the incorporation of M-PMV gRNA into nascent particles. Moreover, the assembly of immature particles of the AEAEA Gag mutant was relocated from the perinuclear region to the plasma membrane. In contrast, an enhancement of the basicity of this region of M-PMV NC (RNRER) caused a substantially more efficient incorporation of gRNA, subsequently resulting in an increase in M-PMV RNRER infectivity. Nevertheless, despite the larger amount of gRNA packaged by the RNRER mutant, the onset of reverse transcription was delayed in comparison to that of the wild type. Our data clearly show the requirement for certain positively charged amino acid residues upstream of the first zinc finger for proper gRNA incorporation, assembly of immature particles, and proceeding of reverse transcription.IMPORTANCE We identified a short sequence within the Gag polyprotein that, together with the zinc finger domains and the previously identified RKK motif, contributes to the packaging of genomic RNA (gRNA) of Mason-Pfizer monkey virus (M-PMV). Importantly, in addition to gRNA incorporation, this basic region (KNKEK) at the N terminus of the nucleocapsid protein is crucial for the onset of reverse transcription. Mutations that change the positive charge of the region to a negative one significantly reduced specific gRNA packaging. The assembly of immature particles of this mutant was reoriented from the perinuclear region to the plasma membrane. On the contrary, an enhancement of the basic character of this region increased both the efficiency of gRNA packaging and the infectivity of the virus. However, the onset of reverse transcription was delayed even in this mutant. In summary, the basic region in M-PMV Gag plays a key role in the packaging of genomic RNA and, consequently, in assembly and reverse transcription.

• MeSH
• buněčné linie MeSH
• genové produkty gag genetika   MeSH
• HEK293 buňky MeSH
• lidé MeSH
• Masonův-Pfizerův opičí virus genetika   fyziologie   MeSH
• mutace genetika   MeSH
• nukleokapsida - proteiny genetika   MeSH
• reverzní transkripce genetika   MeSH
• RNA virová genetika   MeSH
• sekvence aminokyselin genetika   MeSH
• sestavení viru genetika   MeSH
• zinkové prsty genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Assembly of immature retroviral particles is a complex process involving interactions of several specific domains of the Gag polyprotein localized mainly within capsid protein (CA), spacer peptide (SP), and nucleocapsid protein (NC). In the present work we focus on the contribution of NC to the oligomerization of CA leading to assembly of Mason-Pfizer monkey virus (M-PMV) and HIV-1. Analyzing in vitro assembly of substitution and deletion mutants of DeltaProCANC, we identified a "spacer-like" sequence (NC(15)) at the M-PMV NC N terminus. This NC(15) domain is indispensable for the assembly and cannot be replaced with oligomerization domains of GCN4 or CREB proteins. Although the M-PMV NC(15) occupies a position analogous to that of the HIV-1 spacer peptide, it could not be replaced by the latter one. To induce the assembly, both M-PMV NC(15) and HIV-1 SP1 must be followed by a short peptide that is rich in basic residues. This region either can be specific, i.e., derived from the downstream NC sequence, or can be a nonspecific positively charged peptide. However, it cannot be replaced by heterologous interaction domains either from GCN4 or from CREB. In summary, we report here a novel M-PMV spacer-like domain that is functionally similar to other retroviral spacer peptides and contributes to the assembly of immature-virus-like particles.

• MeSH
• buněčné linie MeSH
• DNA primery genetika   MeSH
• DNA virů genetika   MeSH
• Escherichia coli genetika   ultrastruktura   virologie   MeSH
• HIV-1 fyziologie   genetika   MeSH
• lidé MeSH
• Masonův-Pfizerův opičí virus fyziologie   genetika   ultrastruktura   MeSH
• molekulární sekvence - údaje MeSH
• multimerizace proteinu MeSH
• mutageneze MeSH
• nukleokapsida - proteiny fyziologie   genetika   chemie   MeSH
• rekombinantní proteiny genetika   chemie   metabolismus   MeSH
• sekvence aminokyselin MeSH
• sekvence nukleotidů MeSH
• sekvenční homologie aminokyselin MeSH
• sestavení viru fyziologie   genetika   MeSH
• terciární struktura proteinů MeSH
• transmisní elektronová mikroskopie MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH

Despite extensive data demonstrating that immature retroviral particle assembly can take place either at the plasma membrane or at a distinct location within the cytoplasm, targeting of viral precursor proteins to either assembly site still remains poorly understood. Biochemical data presented here suggest that Tctex-1, a light chain of the molecular motor dynein, is involved in the intracellular targeting of Mason-Pfizer monkey virus (M-PMV) polyproteins to the cytoplasmic assembly site. Comparison of the three-dimensional structures of M-PMV wild-type matrix protein (wt MA) with a single amino acid mutant (R55F), which redirects assembly from a cytoplasmic site to the plasma membrane, revealed different mutual orientations of their C- and N-terminal domains. This conformational change buries a putative intracellular targeting motif located between both domains in the hydrophobic pocket of the MA molecule, thereby preventing the interaction with cellular transport mechanisms.

• MeSH
• biologické modely MeSH
• biologický transport MeSH
• buněčná membrána metabolismus   virologie   MeSH
• Cercopithecus aethiops MeSH
• COS buňky MeSH
• cytoplazma metabolismus   MeSH
• dyneiny metabolismus   MeSH
• fenotyp MeSH
• financování organizované MeSH
• genomová oblast t-komplexu MeSH
• jaderné proteiny fyziologie   chemie   metabolismus   MeSH
• lidé MeSH
• Masonův-Pfizerův opičí virus metabolismus   MeSH
• mutace MeSH
• proteiny asociované s mikrotubuly fyziologie   chemie   metabolismus   MeSH
• Retroviridae metabolismus   MeSH
• terciární struktura proteinů MeSH
• vazebná místa MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH

Most retroviruses employ a frameshift mechanism during polyprotein synthesis to balance appropriate ratios of structural proteins and enzymes. To investigate the requirements for individual precursors in retrovirus assembly, we modified the polyprotein repertoire of Mason-Pfizer monkey virus (M-PMV) by mutating the frameshift sites to imitate the polyprotein organization of Rous sarcoma virus (Gag-Pro and Gag-Pro-Pol) or Human immunodeficiency virus (Gag and Gag-Pro-Pol). For the "Rous-like" virus, assembly was impaired with no incorporation of Gag-Pro-Pol into particles and for the "HIV-like" virus an altered morphogenesis was observed. A mutant expressing Gag and Gag-Pro polyproteins and lacking Gag-Pro-Pol assembled intracellular particles at a level similar to the wild-type. Gag-Pro-Pol polyprotein alone neither formed immature particles nor processed the precursor. All the mutants were non-infectious except the "HIV-like", which retained fractional infectivity.

• MeSH
• AIDS opičí virologie   MeSH
• Cercopithecus aethiops MeSH
• COS buňky MeSH
• financování organizované MeSH
• genové produkty gag genetika   MeSH
• genové produkty pol genetika   MeSH
• lidé MeSH
• Masonův-Pfizerův opičí virus genetika   patogenita   MeSH
• messenger RNA genetika   MeSH
• posunová mutace MeSH
• proteosyntéza MeSH
• RNA virová genetika   MeSH
• transfekce MeSH
• virion genetika   patogenita   MeSH
• virové proteiny genetika   MeSH
• virus Rousova sarkomu genetika   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH

Mason-Pfizer monkey virus (M-PMV) Gag protein contains a domain p12 that is unique to this virus (simian retrovirus-3) and its close relatives. The alpha-helical N-terminal half of p12, which contains a leucine zipper-like region, forms ordered structures in E. coli and the C-terminal half can form SDS-resistant oligomers in vitro. Together these properties suggest that p12 is a strong protein-protein interaction domain that facilitates Gag-Gag oligomerization. We have analyzed the oligomerization potential of a panel of p12 mutants, including versions containing substituted dimer, trimer, and tetramer leucine zippers, expressed in bacteria and in the context of the Gag precursor expressed in vitro and in cells. Purified recombinant p12 and its mutants could form various oligomers as shown by chemical cross-linking experiments. Within Gag these same mutants could assemble when overexpressed in cells. In contrast, all the mutants, including the leucine zipper mutants, were assembly defective in a cell-free system. These data highlight the importance of a region containing alternating leucines and isoleucines within p12, but also indicate that this domain's scaffold-like function is more complex than small number oligomerization.

• MeSH
• Cercopithecus aethiops MeSH
• COS buňky MeSH
• financování organizované MeSH
• genové produkty gag genetika   metabolismus   MeSH
• leucinové zipy MeSH
• Masonův-Pfizerův opičí virus fyziologie   genetika   ultrastruktura   MeSH
• molekulární sekvence - údaje MeSH
• mutace MeSH
• rekombinantní proteiny genetika   izolace a purifikace   metabolismus   MeSH
• terciární struktura proteinů MeSH
• transmisní elektronová mikroskopie MeSH
• vazba proteinů MeSH
• virion ultrastruktura   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH