The ZC3H12C ZnF harbors a binding platform for RNA trinucleotide recognition. (A) Electrostatic surface representation of ZC3H12C ZnF-RNA together with a pyrimidine nucleotide (rU3) from the superimposed HsTis11d (ZnF1)-r(UAUU) structure. The superimposed nucleotide occupies the empty groove on the ZnF surface, demonstrating a tri-nucleotide recognition by the ZnF. The ZC3H12C RNA is shown as cartoon, while the added pyrimidine (yellow) is shown as sticks. (B) Molecular interactions of the superimposed uridine with the ZC3H12C ZnF (shown as cartoon). The aligned uridine would form hydrogen bonds (shown as dotted lines) with K449, C436 and C448 residues from the ZFD via its Watson-Crick edge.