scholarly journals The amphotropic and ecotropic murine leukemia virus envelope TM subunits are equivalent mediators of direct membrane fusion: implications for the role of the ecotropic envelope and receptor in syncytium formation and viral entry.

1995 ◽  
Vol 69 (11) ◽  
pp. 7205-7215 ◽  
Author(s):  
J A Ragheb ◽  
H Yu ◽  
T Hofmann ◽  
W F Anderson
Keyword(s):  
Membrane Fusion ◽  
Viral Entry ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Syncytium Formation ◽  
Virus Envelope ◽  
Murine Leukemia

scholarly journals The Role of the Membrane-spanning Domain Sequence in Glycoprotein-mediated Membrane Fusion

1999 ◽  
Vol 10 (9) ◽  
pp. 2803-2815 ◽  
Author(s):  
Gwen M. Taylor ◽  
David Avram Sanders
Keyword(s):  
Membrane Fusion ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Envelope Proteins ◽  
Viral Fusion ◽  
Virus Envelope ◽  
Membrane Spanning ◽  
Membrane Spanning Domains ◽  
Murine Leukemia

The role of glycoprotein membrane-spanning domains in the process of membrane fusion is poorly understood. It has been demonstrated that replacing all or part of the membrane-spanning domain of a viral fusion protein with sequences that encode signals for glycosylphosphatidylinositol linkage attachment abrogates membrane fusion activity. It has been suggested, however, that the actual amino acid sequence of the membrane-spanning domain is not critical for the activity of viral fusion proteins. We have examined the function of Moloney murine leukemia virus envelope proteins with substitutions in the membrane-spanning domain. Envelope proteins bearing substitutions for proline 617 are processed and incorporated into virus particles normally and bind to the viral receptor. However, they possess greatly reduced or undetectable capacities for the promotion of membrane fusion and infectious virus particle formation. Our results imply a direct role for the residues in the membrane-spanning domain of the murine leukemia virus envelope protein in membrane fusion and its regulation. They also support the thesis that membrane-spanning domains possess a sequence-dependent function in other protein-mediated membrane fusion events.

scholarly journals Role of intron-contained sequences in formation of moloney murine leukemia virus env mRNA.

1984 ◽  
Vol 4 (11) ◽  
pp. 2289-2297 ◽  
Author(s):  
L S Hwang ◽  
J Park ◽  
E Gilboa
Keyword(s):  
Splice Site ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Splice Junction ◽  
Moloney Murine Leukemia Virus ◽  
Expression Vectors ◽  
Virus Envelope ◽  
Cellular Genes ◽  
Murine Leukemia

Formation of the Moloney murine leukemia virus envelope mRNA involves the removal of a 5,185-base pair-long intron. Deletion analysis of two Moloney murine leukemia virus-derived expression vectors revealed the existence of two short regions within the viral intron which are required for the efficient formation of the spliced RNA species. One region was present upstream from the 3' splice junction, extended at least 85 nucleotides beyond the splice site, and was not more than 165 nucleotides long. As yeast polymerase II introns, the Moloney murine leukemia virus intron contains the sequence 5'-TACTAAC-3' 15 nucleotides upstream from the 3' splice site. A second region located in the middle of the intron, within a 560-nucleotide-long sequence, was also essential for formation of the spliced RNA species. The efficient splicing of the env mRNA in the absence of expression of viral genes raises the possibility that similar mechanisms are used to remove introns of (some) cellular genes.

scholarly journals Asymmetric Requirement for Cholesterol in Receptor-Bearing but Not Envelope-Bearing Membranes for Fusion Mediated by Ecotropic Murine Leukemia Virus

2002 ◽  
Vol 76 (13) ◽  
pp. 6701-6709 ◽  
Author(s):  
Xiongbin Lu ◽  
Ying Xiong ◽  
Jonathan Silver
Keyword(s):  
Murine Leukemia Virus ◽  
Mammalian Cells ◽  
Insect Cells ◽  
Leukemia Virus ◽  
Cell System ◽  
Membrane Rafts ◽  
Cell Physiology ◽  
Virus Envelope ◽  
Murine Leukemia

ABSTRACT We show that fusion mediated by ecotropic murine leukemia virus envelope is dependent on cholesterol in receptor-bearing membranes. The effect is >10 times larger in insect cells than mammalian cells, probably because the former can be more extensively depleted of cholesterol. The fact that cholesterol is apparently not needed in envelope-bearing membranes suggests that it plays a role in an asymmetric step in membrane fusion and argues against a class of models in which cholesterol is important in symmetric fusion intermediates. The insect cell system has promise for clarifying the role of membrane rafts in other aspects of cell physiology.

Role of intron-contained sequences in formation of moloney murine leukemia virus env mRNA

1984 ◽  
Vol 4 (11) ◽  
pp. 2289-2297
Author(s):  
L S Hwang ◽  
J Park ◽  
E Gilboa
Keyword(s):  
Splice Site ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Splice Junction ◽  
Moloney Murine Leukemia Virus ◽  
Expression Vectors ◽  
Virus Envelope ◽  
Cellular Genes ◽  
Murine Leukemia

Formation of the Moloney murine leukemia virus envelope mRNA involves the removal of a 5,185-base pair-long intron. Deletion analysis of two Moloney murine leukemia virus-derived expression vectors revealed the existence of two short regions within the viral intron which are required for the efficient formation of the spliced RNA species. One region was present upstream from the 3' splice junction, extended at least 85 nucleotides beyond the splice site, and was not more than 165 nucleotides long. As yeast polymerase II introns, the Moloney murine leukemia virus intron contains the sequence 5'-TACTAAC-3' 15 nucleotides upstream from the 3' splice site. A second region located in the middle of the intron, within a 560-nucleotide-long sequence, was also essential for formation of the spliced RNA species. The efficient splicing of the env mRNA in the absence of expression of viral genes raises the possibility that similar mechanisms are used to remove introns of (some) cellular genes.

Characterization of R peptide of murine leukemia virus envelope glycoproteins in syncytium formation and entry

2007 ◽  
Vol 152 (12) ◽  
pp. 2169-2182 ◽  
Author(s):  
Y. Kubo ◽  
C. Tominaga ◽  
H. Yoshii ◽  
H. Kamiyama ◽  
C. Mitani ◽  
...  
Keyword(s):  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Syncytium Formation ◽  
Envelope Glycoproteins ◽  
Virus Envelope ◽  
Murine Leukemia

scholarly journals Mutations in the Cytoplasmic Tail of Murine Leukemia Virus Envelope Protein Suppress Fusion Inhibition by R Peptide

2001 ◽  
Vol 75 (5) ◽  
pp. 2337-2344 ◽  
Author(s):  
Min Li ◽  
Chinglai Yang ◽  
Richard W. Compans
Keyword(s):  
Amino Acids ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Cytoplasmic Tail ◽  
Syncytium Formation ◽  
Inhibitory Effect ◽  
Fusion Activity ◽  
Virus Envelope ◽  
Env Protein ◽  
Murine Leukemia

ABSTRACT During viral maturation, the cytoplasmic tail of the murine leukemia virus (MuLV) envelope (Env) protein undergoes proteolytic cleavage by the viral protease to release the 16-amino-acid R peptide, and this cleavage event activates the Env protein's fusion activity. We introduced Gly and/or Ser residues at different positions upstream of the R peptide in the cytoplasmic tail of the Friend MuLV Env protein and investigated their effects on fusion activity. Expression in HeLa T4 cells of a mutant Env protein with a single Gly insertion after I619, five amino acids upstream from the R peptide, induced syncytium formation with overlaid XC cells. Env proteins containing single or double Gly-Ser insertions after F614, 10 amino acids upstream from the R peptide, induced syncytium formation, and mutant proteins with multiple Gly insertions induced various levels of syncytium formation between HeLa T4 and XC cells. Immunoprecipitation and surface biotinylation assays showed that most of the mutants had surface expression levels comparable to those of the wild-type or R peptide-truncated Env proteins. Fluorescence dye redistribution assays also showed no hemifusion in the Env proteins which did not induce fusion. Our results indicate that insertion mutations in the cytoplasmic tail of the MuLV Env protein can suppress the inhibitory effect of the R peptide on membrane fusion and that there are differences in the effects of insertions in two regions in the cytoplasmic tail upstream of the R peptide.

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