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Identification of FBXO25-interacting proteins using an integrated proteomics approach


FBXO25 is one of the 68 human F-box proteins that serve as specificity factors for a family ofubiquitin ligases composed of s-phase-kinase associated protein 1, really interesting new gene-box 1, Cullin 1, and F-box protein (SCF1) at are involved in targeting proteins for destruction across the ubiquitin proteasome system. We recently reported that the FBXO25 protein accumulates in novel subnuclear structures named FBXO25-associated nuclear domains (FAND). Combining two-step affinity purification followed by MS with a classical two-hybrid screen, we identified 132 novel potential FBXO25 interacting partners. One of the identified proteins, b-actin, physically interacts through its N-terminus with FBXO25 and is enriched in the FBXO25 nuclear compartments. Inhibitors of actin polymerization promote a significant disruption of FAND, indicating that they are compartments influenced by the organizational state of actin in the nucleus. Furthermore, FBXO25 antibodies interfered with RNA polymerase II transcription in vitro. Our results open new perspectives for the derstandingof this novel compartment and its nuclear functions. (AU)