ASSEMBLY OF A TEMPERATURE-SENSITIVE MUTANT OF RAUSCHER MURINE LEUKEMIA-VIRUS AT THE CELL-SURFACE INDUCED BY LOW-TEMPERATURE AND BY LIGANDS

NIH/3T3 mouse fibroblasts, infected with a Rauscher murine leukemia virus temperature-sensitive mutant (ts25) defective in assembly of budding particles at 39°, produce virus at the cell surface when the temperature is shifted rapidly to 0°. Virus buds are not assembled within the first 10 min at 0° and gradually increase in number and degree of development over a 2-hr period. However, release of infectious virus could not be demonstrated at 0° and might, therefore, be an energy-dependent process. Significant budding activity was also induced at the nonpermissive temperature by incubating cells with 0.25% glutaraldehyde or with antiserum to the major virus envelope glycoprotein, gp70. Anti-gp70 serum may induce budding by promoting aggregation of gp70-containing molecular assemblies and, consequently, association of core components in some transmembrane fashion. Induction of virus assembly with glutaraldehyde might occur as a results of nonspecific cross-linking of membrane proteins. These results suggest that procedures commonly used to minimize ligand-induced redistribution of cell surface molecules, i.e., labeling at low temperatures or after mild aldehyde fixation, may not immobilize certain membrane-associated molecules. © 1979.