Figure 8.

Schematic representation of the binding of RRM1, RRM2 and T187 to RNA substrates. (a) EDEN7 is able to accommodate two RRM1s on adjacent UGU sites, but only a single RRM2 can bind to the same sequence, suggesting specificity for a UGUU binding site. (b) EDEN7 is too short to bind the two RRMs of T187 in tandem, instead we observe an interaction through RRM1 which could be at either of the two UGU sites (one shown). (c) Binding of T187 to both sites of the consensus GRE sequence (EDEN11) with RRM2 bound at the 5′-terminal UGUU site. The spacer sequence of 5 nt between the tandem UGU sites results in high affinity binding. (d) Possible interaction of full-length CELF1 with a GU-rich substrate with RRM1 and RRM2 bound as for the consensus sequence in (c); the long linker between RRM2 and RRM3 permits considerable conformational flexibility in binding a third UGU site up or down stream (position of arrows), or even to the looped-out spacer sequence between the RRM1 and RRM2 binding sites.