Transforming Activity of Murine Herpesvirus 68 Putative Growth Factor Is Related to the Ability to Change Cytoskeletal Structure.

Murine herpesvirus 68 (MHV-68) can transform cells in vitro and in vivo. We investigated putative murine herpesvirus growth factors (MHGFs) obtained by the separation of cell-free media from MHV-68-transformed cells on an FPLC Sephadex G15 column. The transforming activity of the MHGFA fraction was related to depolymerization of actin, disruption of the microtubule network, and punctate-reticular changes of the Golgi. The MHGFW fraction had only repressing activity on the transformed phenotype. Incubation of MRC-5 cells with MHGFW resulted in reticular changes of the Golgi apparatus, minor depolymerization of actin filaments, and no detectable changes of the microtubule network. Reorganization of the actin cytoskeleton is associated with oncogenesis. Further study of the MHGFs from herpesviruses and proteins responsible for changes in the organization of the cytoskeleton could give insight into the cell transformation mechanism and oncogenesis.