Fig. 1.

Representation of putative alternative PAQosomes. The PAQosome (originally R2TP/PFDL complex) exists in different flavors generated through the differential integration of homologous subunits (e.g., RPAP3 vs. SPAG1, PIH1D1 vs. PIH1D2, etc). The results of Martino et al.⁹ suggest that up to three RPAP3 may bind the RUVBL1-RUVBL2 scaffold, although this has not been confirmed in vivo. The existence of alternative PAQosomes along with the use of various specificity factors (adaptors) can theoretically multiply by many fold the number of clients they can act upon during quaternary structure arrangement, playing a central role in building up the interactome (protein complexes and networks). Whether alternative subunits modify the overall organization and composition of the PAQosome remains to be addressed experimentally