UBAP2L‐dependent coupling of PLK1 localization and stability during mitosis

Abstract

PLK1 is an important regulator of mitosis whose protein levels and activity fluctuate during the cell cycle. PLK1 dynamically localizes to various mitotic structures to regulate chromosome segregation. However, the signaling pathways linking localized PLK1 activity to its protein stability remain elusive. Here, we identify the Ubiquitin-Binding Protein 2-Like (UBAP2L) that controls both the localization and the protein stability of PLK1. We demonstrate that UBAP2L is a spindle-associated protein whose depletion leads to severe mitotic defects. UBAP2L-depleted cells are characterized by increased PLK1 protein levels and abnormal PLK1 accumulation in several mitotic structures such as kinetochores, centrosomes and mitotic spindle. UBAP2L-deficient cells exit mitosis and enter the next interphase in the presence of aberrant PLK1 kinase activity. The Cterminal domain of UBAP2L mediates its function on PLK1 independently of its role in stress response signaling. Importantly, the mitotic defects of UBAP2L-depleted cells are largely rescued by chemical inhibition of PLK1. Overall, our data suggest that UBAP2L is required to fine-tune the ubiquitin-mediated PLK1 turnover during mitosis as a means to maintain genome fidelity.

UBAP2L ensures homeostasis of nuclear pore complexes at the intact nuclear envelope

“…S1, L and P ; and Fig. S3 E ), which is in agreement with our published findings ( Guerber et al, 2023 ). These results suggest that UBAP2L regulates Nups localization and possibly their assembly without affecting the size of the nucleus or the length of the G1 phase.…”

“…Cellular fractionation experiments confirmed that UBAP2L could be found in the nucleus in interphase ( Fig. S1 F ), in accordance with our published findings ( Guerber et al, 2023 ). NE localization of endogenous UBAP2L was detected in early prophase, late telophase, and in G1 cells ( Fig.…”

“…To understand if UBAP2L regulates Nups, we used two clonal HeLa cell lines with CRISPR/Cas9-mediated deletion of the UBAP2L gene, which we previously characterized ( Guerber et al, 2023 ). As expected ( Cirillo et al, 2020 ; Huang et al, 2020 ; Youn et al, 2018 ), deletion of UBAP2L inhibited formation of SGs upon stress ( Fig.…”

“…3 J ), suggesting that UBAP2L does not regulate total protein levels but rather Nups localization during interphase. Owing to the fact that UBAP2L deletion can delay mitotic exit ( Guerber et al, 2023 ), which could theoretically influence the length of the G1 phase and, indirectly, the localization of Nups, we have arrested UBAP2L KO cells in G1 using lovastatin ( Rao et al, 1999 ) and observed accumulation of cytoplasmic Nup foci and reduced NE intensity of mAb414-reactive Nups ( Fig. S1, I–K ), but no changes in nuclear size ( Fig.…”

Calreticulin and JAK2V617F driver mutations induce distinct mitotic defects in myeloproliferative neoplasms

“…The effect of CALRdel52 transduction is opposite to that of JAK2V617F for the localization of MAD1, CDC20, cyclin B1, but shows the same tendency for BubR1 and MPS1, suggesting an alteration in the upstream regulatory network. We hypothesized that the kinetochore recruitment imbalances of these SAC factors could result from abnormal expression of master mitotic regulators like PLK1 [50][51][52][53] and / or PP2A [54][55][56][57][58], which control mitotic kinetochore integrity and SAC signaling. However, we did not detect signi cant changes in the whole protein expression levels either PLK1 or PP2A by Western blotting, which suggest that CALRdel52 or JAK2V617F mutations do not affect the expression of these master mitotic regulators in murine 32D cells (Supplementary Fig.…”