Differential response to cytochalasin B among cells transformed by DNA and RNA tumor viruses.

Mouse, hamster, rat, human, and chick cells were transformed by RNA and DNA tumor viruses: simian virus 40, adenovirus type 7, Kirsten mouse sarcoma virus (Ki-MuSV), Moloney mouse sarcoma virus, and Rous sarcoma virus. All cultures of transformed cells grew to high concentration densities. Normal and transformed cells were treated with cytochalasin B (CB) at concentrations preventing cytoplasmic cleavage. Cells altered by DNA tumor viruses responded to CB with numerous nuclear divisions resulting in highly multinucleated cells. All but one line of cells transformed by RNA tumor viruses responded to CB with usually only one and occasionally two nuclear divisions. Only binucleated cells were formed. One clone of CB-treated BALB/c mouse embryo fibroblasts transformed by Ki-MuSV showed numerous cells with four and five nuclei. HOWEVER, IN CONTRASt to cells transformed by DNA viruses, few cells had seven or more nuclei. These results suggest that, in the presence of CB, cells transformed by DNA tumor viruses show uncontrolled nuclear division, whereas cells tranformed by RNA tumor viruses show controlled nuclear division.