FBXO21 mediates the ubiquitylation and proteasomal degradation of EID1

Abstract

Although identification of substrates for ubiquitin ligase (E3) is important for understanding its biological functions, detection of the interaction between an E3 and its substrates has remained challenging. We recently developed a new approach, termed differential proteomics-based identification of ubiquitylation substrates (DiPIUS), for the discovery of substrates of a given E3 ligase. We have now applied this approach to an uncharacterized human F-box protein, FBXO21, which serves as the substrate-recognition subunit of a SKP1-CUL1-F-box protein (SCF)-type E3, thereby identifying EID1 (EP300-interacting inhibitor of differentiation 1) as a candidate substrate. The central and COOH-terminal portion of FBXO21 was found to interact with the COOH-terminal region of EID1 in transfected cells. Over-expression of FBXO21 resulted in the down-regulation of EID1, whereas disruption of the FBXO21 gene with the CRISPR/Cas9 system stabilized EID1 and led to its accumulation in both the cytoplasm and nucleus. An in vitro ubiquitylation assay showed that EID1 is a direct substrate of SCF FBXO21 . Collectively, our results suggest that EID1 is a bona fide substrate of FBXO21 and that the control of EID1 abundance by SCF FBXO21 might affect the transcriptional repression activity of EID1.

Peptidic degron in EID1 is recognized by an SCF E3 ligase complex containing the orphan F-box protein FBXO21

“…The same conclusion has now been reported by another group working in parallel (23,24). Despite earlier reports (5, 18), we have thus far not confirmed a physiological role for MDM2 in EID1 ubiquitylation, although MDM2 might polyubiquitylate EID1 under conditions not tested here.…”

X‐ray crystal structure of Escherichia coli HspQ, a protein involved in the retardation of replication initiation

“…ClpS1‐ClpF mutually stimulated the association of hetero‐oligomeric Clp protease in plant chloroplast, resulting in enhancing degradation by Clp protease. Moreover, YccV domain was conserved in F‐Box 21, which was used as an adaptor protein to recognize and recruit target proteins in ubiquitin ligases system for proteasome degradation . Therefore, it is likely that YccV domains have a role in the interaction with basic target proteins and in the recruitment of target proteins to a degradation system in the cell.…”

F-box protein interactions with the hallmark pathways in cancer

“…SCF(Fbxo21) ubiquitinates and degrades a protein called E1A-like inhibitor of differentiation 1 (EID1) (67), which binds to TFs and co-activators, including pRb, p300 and CBP. Together, this prevents MyoD transactivation, which is a master regulator of muscle specification (68).…”