FIGURE 4.

The most distal DAD-like motif in FRL3 is required for autoregulation. A, alignment of the FRL1, -2, and -3 C-terminal domains. Two WH2/DAD-like motifs (blue) are present in the C termini of FRL2 and FRL3. Basic residues are highlighted in red. B and C, FRL3.F1F2.1045 (red)-induced stress fiber (green) formation is largely unaffected by co-expression of FRL3N (white) (94%, n = 102 versus 72%, n = 101). D, deletion of the FRL3 DAD domain does not significantly affect FRL3.F1F2 activity. Inset, relative levels of expression of FRL3.F1F2 and FRL3.F1F2.1045, as determined by immunoblotting using the same exposure of the same gel. Reporter gene activity was standardized to activation induced by expression of an SRF-VP16 control fusion protein. Error bars, S.E., n = 3. E, SRF reporter gene activation by FRL2.FH2.1045 is not significantly inhibited by FRL2N or FRL3N. Reporter gene activation in the absence of inhibitor was standardized to 100%. Error bars, S.E., n = 3. F, schematic of FRL3 derivatives.