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J. Virol., 05 1997, 3613-3619, Vol 71, No. 5
MM Januszeski, PM Cannon, D Chen, Y Rozenberg and WF Anderson
The cytoplasmic tail of the immature Moloney murine leukemia virus (MoMuLV)
envelope protein is approximately 32 amino acids long. During viral
maturation, the viral protease cleaves this tail to release a 16-
amino-acid R peptide, thereby rendering the envelope protein fusion
competent. A series of truncations, deletions, and amino acid substitutions
were constructed in this cytoplasmic tail to examine its role in fusion and
viral transduction. Sequential truncation of the cytoplasmic tail revealed
that removal of as few as 11 amino acids resulted in significant fusion
when the envelope protein was expressed in NIH 3T3 cells, similar to that
seen following expression of an R- less envelope (truncation of 16 amino
acids). Further truncation of the cytoplasmic tail beyond the R-peptide
cleavage site toward the membrane- spanning region had no additional effect
on the level of fusion observed. In contrast, some deletions and
nonconservative amino acid substitutions in the membrane-proximal region of
the cytoplasmic tail (residues L602 to F605) reduced the amount of fusion
observed in XC cell cocultivation assays, suggesting that this region
influences the fusogenicity of full-length envelope protein. Expression of
the mutant envelope proteins in a retroviral vector system revealed that
decreased envelope-mediated cell-cell fusion correlated with a decrease in
infectivity of the resulting virions. Additionally, some mutant envelope
proteins which were capable of mediating cell-cell fusion were not
efficiently incorporated into retroviral particles, resulting in defective
virions. The cytoplasmic tail of MoMuLV envelope protein therefore
influences both the fusogenicity of the envelope protein and its
incorporation into virions.
Copyright © 1997, American Society for Microbiology
Functional analysis of the cytoplasmic tail of Moloney murine leukemia virus envelope protein
Norris Cancer Center, University of Southern California School of Medicine, Los Angeles 90033, USA.
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