Molecular and functional characterisation of the novel nuclear basket protein ZC3HC1

The nuclear basket (NB) is a fibrillar structure anchored to the nuclear pore complex. The NB scaffold is formed by the coiled-coil dominated protein TPR. Other NB-resident proteins use the NB only as a binding platform without acting as a structural element themselves. We found that ZC3HC1 is a novel, bona fide component of the NB, which is required for the recruitment of TPR subpopulations to the NB, where ZC3HC1 acts as a linker to establish stable interconnections between TPR polypeptides positioned at the NB and to maintain the integrity of these assemblies. Consequently, ZC3HC1 allows for a higher complexity of the NB than previously anticipated. In addition, we characterised the molecular properties of ZC3HC1 that are prerequisites for its interaction with the NB and TPR polypeptides. We further revealed the evolutionary conservation of the TPR:ZC3HC1 interaction, exemplified by demonstrating that Pml39p is the structural and functional homologue of ZC3HC1 in Saccharomyces cerevisiae.