Movie S2.

RapR-Src induces Rac1 activation in HeLa cells. A HeLa cell coexpressing RapR-Src-as2-mCherry-myc and Rac1-FLARE (transient transfection) and iPEP-GFP(Y66S)-FRB (adenoviral infection) was imaged for 2 h every 2 min. Rapamycin (500 nM) was added after 30 min (indicated by appearance of “Rapamycin Added”), and DMSO was added after 15 min (indicated by appearance of “DMSO Added”). The movie shows FRET/CFP signal ratio images of Rac1-FLARE biosensor in a living cell. Warmer colors reflect higher local activity of Rac1.