Fig. 7. Rho family GTPases and actin in BCR-mediated SRF activation. (A) Differential requirement for Rho, Rac and CDC42. SRF and NFAT transcriptional activity was determined in WT DT40 cells transfected with empty vector (control), dominant negative RhoA, Rac or CDC42. These dominant negative GTPases did not affect BCR-induced Elk-1 activation (data not shown). (B) A role for actin. SRF and NFAT transcriptional activity was determined in WT DT40 cells transfected with GFP (control) or actin–GFP (actin).