Fig. 4. Oncogenic activation of Sbf1 by N-terminal deletions. (A) Representative focus-forming assay shows that the N111 mutant, but not wild-type, Sbf1 induces foci in monolayers of stably transfected NIH 3T3 cells. (B) Bar graph indicates focus-forming activity of mutant Sbf1 proteins. Data are the average of three experiments performed in triplicate.