A diverse interactome of the molecular chaperone CCT/TRiC monomers.

The molecular chaperone CCT is essential in eukaryotes where it is required for the folding of actin and tubulin. Extensive studies have defined interactomes of the assembled CCT oligomer where binding partners include obligate folding substrates, opportunistic substrates and regulatory proteins. In addition to folding, the CCT oligomer acts as a sequestering complex and several of the individual CCT subunits, when monomeric, are known to possess functions distinct from folding. Here the first interactome of the individual subunits as monomers is defined by yeast 2-hybrid screening, revealing an array of subunit-specific interaction partners linked to diverse cellular functions. We identify, by live cell imaging/ fluorescence microscopy following siRNA depletions, CCT subunit-specific effects on cell cycle progression and show that CCT5 influences localisation of KNL1 to the kinetochore. Our results reveal the extent of CCT monomer interactions, which are essential for a complete understanding of the cellular functions of CCT.