Identification of a cytoplasmic targeting/retention signal in a retroviral Gag polyprotein.
Retroviral capsid assembly can occur by either of two distinct morphogenic processes: in type C viruses, the capsid assembles and buds at the plasma membrane, while in type B and D viruses, the capsid assembles within the cytoplasm and is then transported to the plasma membrane for budding. We have previously reported that a single-amino-acid substitution of a tryptophan for an arginine in the matrix protein (MA) of Mason-Pfizer monkey virus (MPMV) converts its capsid assembly from that of a type D retrovirus to that of the type C viruses (S. S. Rhee and E. Hunter, Cell 63:77-86, 1990). Here we identify a region of 18 amino acids within the MA of MPMV that is responsible for type D-specific morphogenesis. Insertion of these 18 amino acids into the MA of type C Moloney murine leukemia virus causes it to assemble an immature capsid in the cytoplasm. Furthermore, fusion of the MPMV MA to the green fluorescent protein resulted in altered intracellular targeting and a punctate accumulation of the fusion protein in the cytoplasm. These 18 amino acids, which are necessary and sufficient to target retroviral Gag polyproteins to defined sites in the cytoplasm, appear to define a novel mammalian cytoplasmic targeting/retention signal.
Choi
G
G
Laboratory of Molecular Virology, Samsung Biomedical Research Institute, Seoul, Korea.
Park
S
S
Choi
B
B
Hong
S
S
Lee
J
J
Hunter
E
E
Rhee
S S
SS
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D019677:Artificial Gene Fusion; D019556:COS Cells; D002213:Capsid / Q000096:biosynthesis; D003593:Cytoplasm / Q000378:metabolism / Q000648:ultrastructure; D015683:Gene Products, gag / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D007424:Intracellular Fluid / Q000378:metabolism; D008164:Luminescent Proteins; D016093:Mason-Pfizer monkey virus / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D008979:Moloney murine leukemia virus / Q000235:genetics / Q000378:metabolism; D016296:Mutagenesis; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000096:biosynthesis
D015683:Gene Products, gag; D008164:Luminescent Proteins; D021382:Protein Sorting Signals; D011506:Proteins; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins; D049452:Green Fluorescent Proteins