Transformation by the oncogenic latent membrane protein correlates with its rapid turnover, membrane localization, and cytoskeletal association

Abstract

The latent membrane protein (LMP) of Epstein-Barr virus (EBV) has a short half-life (V. R. Baichwal and B. Sugden, J. Virol, 61:866-875, 1987; K.P. Mann and D. Thorley-Lawson, J. Virol, 61:2100-2108, 1987), is localized in patches in the membrane (D. Liebowitz, D. Wang, and E, Kieff, J. Virol, 58:233-237, 1986), and associates with the cytoskeleton in EBV-immortalized B lymphocytes (D. Liebowitz, R. Kopan, E. Fuchs, J. Sample, and E. Kieff, Mol. Cell. Biol. 7:2299-2308, 1987; K. P. Mann and D. Thorley-Lawson, J. Virol. 61:2100-2108, 1987). Deletion mutants of LMP that are either positive or negative in the induction both of anchorage-independent growth of BALB/c 3T3 cells (V. R. Baichwal and B. Sugden, Oncogene 4:67-74, 1989) and of cytotoxicity in a variety of cells (W. Hammerschmidt, B. Sugden, and V. R. Baichwal, J. Virol. 63:2469-2475, 1989) have been studied to identify the biochemical properties of this protein that correlate with its effects on cell growth. Mutant LMP proteins that are metabolically stable, do not associate with the cytoskeleton, and exhibit a diffuse plasma membrane localization also do not induce anchorage-independent growth in rodent cells or cytotoxicity in B lymphoblastoid cells. In contrast, a mutant of LMP that is functionally identical to the wild-type protein has a half-life, membrane localization, and cytoskeletal association similar or identical to those of LMP. These results are consistent with the hypothesis that LMP's rapid turnover, association with the cytoskeleton, and patching in the membrane are required for it to affect cell growth.