Intracellular transport and leukemogenicity of spleen focus-forming virus envelope glycoproteins with altered transmembrane domains.

Friend murine spleen focus-forming virus (SFFV) encodes a glycoprotein designated gp52, which is responsible for the leukemogenic properties of the virus. gp52 lacks a cytoplasmic domain and is defective in its transport to the cell surface. We constructed a chimeric envelope gene which codes for a molecule with an external domain derived from the SFFV envelope gene and membrane-spanning and cytoplasmic domains derived from the Friend murine leukemia virus envelope gene. Like gp52, the chimeric protein was defective in its transport to the cell surface, indicating that the absence of a cytoplasmic tail is not responsible for the defective intracellular transport of SFFV gp52. However, unlike wild-type SFFV, the chimeric SFFV genome failed to induce erythroleukemia in adult mice. The results indicate that the altered membrane-spanning domain, lack of a detectable cytoplasmic tail in gp52, or both factors are prerequisites for the erythroleukemia-inducing properties of SFFV but are not responsible for the block in intracellular transport of the glycoprotein.