Reduced Rac activation in response to SCF in RhoH-transduced progenitor cells. Vector- and RhoH-transduced progenitor (c-Kit⁺, EGFP⁺) cells were stimulated with 100 ng/mL SCF for 0 to 5 minutes and used in a PAK1 effector pull-down assay. The levels of the active, GTP-bound Rac proteins were examined by immunoblot analysis using the anti-Rac antibody detecting both Rac1 and Rac2. The levels of total Rac proteins in whole-cell lysates were examined in parallel. One representative blot of 3 experiments is shown.