FBXO38 Ubiquitin Ligase Controls Centromere Integrity via ZXDA/B Stability

Abstract

Alterations in the gene encoding the E3 ubiquitin ligase substrate receptor FBXO38 have been associated with several diseases, including early-onset motor neuronopathy. However, the cellular processes affected by the enzymatic action of FBXO38 are not yet known. Here, we identify the zinc finger proteins ZXDA/B as its interaction partners. FBXO38 controls the stability of ZXDA/B proteins via ubiquitination and proteasome-dependent degradation. We show that ZXDA/B proteins associate with the centromeric protein CENP-B and that the interaction between ZXDA/B and FBXO38 or CENP-B is mutually exclusive. Functionally, ZXDA/B factors control the protein level of chromatin-associated CENP-B. Furthermore, their inappropriate stabilization leads to upregulation of CENP-A and CENP-B positive centromeric chromatin. Thus we demonstrate a previously unknown role of cullin-dependent protein degradation in the control of centromeric chromatin integrity.

FBXO38 does not control PD-1 stability

“…We pretreated the cells with (MLN4924) to avoid the degradation of PD-1, which could be potentially caused by FBXO38 overexpression. Consistent with our previous observations 3,4 , FBXO38 interacted with its substrate ZXDB, and deletion of either its C-terminus or its F-box motif disrupted this interaction (Fig. 1b).…”

“…Meng et al overexpressed FBXO38 in HEK293FT cells to enhance PD-1 degradation. However, we have previously shown that FBXO38 overexpression does not result in forced degradation of its substrate 3 . Accordingly, we observed only a modest decrease in ZXDB protein level and no changes in PD-1.…”

“…1a) 6 . Our previous studies demonstrated that FBXO38 is localized in the nucleus both in cultured cells and in vivo 3,4 . This is a consequence of its strong nuclear localization signals.…”

“…Prepared cDNAs were cloned into the pSBtet-Pur plasmid using SfiI restriction sites. FBXO38-containing plasmids were created as described previously 3 . Briefly, human FBXO38 cDNA (Origene #RC204380) was cloned into pcDNA3.1 containing N-terminal twinStrepII-FLAG-tag (NSF).…”

“…Its gene has been found to be mutated in several families with early-onset distal hereditary motor neuronopathy 2 . SCF FBXO38 ubiquitin ligase controls the stability of ZXDB, a nuclear factor associated with the centromeric chromatin protein CENP-B 3 . Moreover, the loss of FBXO38 results in growth retardation and defect in spermatogenesis characterized by deregulation of the Sertoli cell transcription program and centromere integrity 4 .…”