Glucocorticoid-dependent maturation of viral proteins in mouse lymphoma cells: isolation of defective and hormone-independent cell variants.

Maturation of mouse mammary tumor virus proteins is dependent on glucocorticoid hormones in W7MG1, a stably infected mouse T-lymphosarcoma cell line derived from WEH17. We used an immunological procedure to select variant cell lines with altered levels of viral glycoproteins on the cell surface. One variant, W7M329a, expressed lower-than-normal levels of the major viral glycoprotein, gp52env, on the cell surface before and after exposure to hormone. Two other variants, W7M302b and W7M326.4, expressed elevated levels of gp52env on the cell surface even in the absence of hormone. Analysis of the levels and/or rates of synthesis of viral RNA and glycoproteins before and after hormone treatment indicated that the variant phenotypes resulted from changes in posttranslational steps of viral gene expression. The hormone-independent maturation of MMTV proteins is a novel variant phenotype that has not previously been reported.