This is an unusual zinc-finger family, and is represented by fingers 5-7 of Nab2. Nab2 ZnF5-7 are zinc-fingers of the type C-x8-C-x5-C-x3-H. Nab2 ZnFs function in the generation of export-competent mRNPs. Mab2 is a conserved polyadenosine-RNA-binding Zn finger protein required for both mRNA export and polyadenylation regulation and becomes attached to the mRNP after splicing and during or immediately after polyadenylation. The three ZnFs, 5-7, have almost identical folds and, most unusually, associate with one another to form a single coherent structural unit. ZnF5-7 bind to eight consecutive adenines, and chemical shift perturbations identify residues on each finger that interact with RNA [1].

1: Structural basis for polyadenosine-RNA binding by Nab2 Zn fingers and its function in mRNA nuclear export. Brockmann C, Soucek S, Kuhlmann SI, Mills-Lujan K, Kelly SM, Yang JC, Iglesias N, Stutz F, Corbett AH, Neuhaus D, Stewart M; Structure. 2012;20:1007-1018. PMID:22560733