Fig. 5. FBF binds specifically to elements in fog-1 and fog-3 3'UTRs. (A) Putative FBF binding elements (FBEs) in fog and fem 3'UTRs; black triangles, elements that bind in vitro; gray triangles, elements that do not bind in vitro. (B) Nucleotide sequence of predicted FBF binding elements. Sequences are aligned by conserved UGU motif (bold). Mutated nucleotides are lowercase. [UUUUU towards 3' end of fog-1 FBE bc RNA was disrupted to increase expression in three-hybrid system (indicated by `a').] (C) Yeast three-hybrid assay. (D) Yeast three-hybrid results. Error bars represent standard deviation of at least four repetitions. gld-1 FBEa, element in gld-1 3'UTR (Bernstein et al., 2005; Crittenden et al., 2002); fem-3 PME, element in fem-3 3'UTR (Zhang et al., 1997), which is called fem-3 FBEa in A. (E) FBF-2 binds FBEs in fog-1 and fog-3 3'UTRs. Protein concentrations were 0.5 nM, 1 nM and 5 nM, then consecutively doubled to reach 640 nM. Apparent binding constants are shown below each shift.