UV-induced degradation of securin is mediated by SKP1-CUL1-βTrCP E3 ubiquitin ligase

Abstract

Securin is a chaperone protein with bifunctional properties. It binds to separase to inhibit premature sister chromatid separation until the onset of anaphase, and it also takes part in cell-cycle arrest after UV irradiation. At metaphase-to-anaphase transition, securin is targeted for proteasomal destruction by the anaphase-promoting complex or cyclosome (APC/C), allowing activation of separase. However, although securin is reported to undergo proteasome-dependent degradation after UV irradiation, the ubiquitin ligase responsible for securin ubiquitylation has not been well characterized. In this study, we show that UV radiation induced a marked reduction of securin in both the nucleus and cytoplasm. Moreover, we show that GSK-3β inhibitors prevent securin degradation, and that CUL1 and βTrCP are involved in this depletion. We also confirmed that SKP1-CUL1-βTrCP (SCFβTrCP) ubiquitylates securin in vivo, and identified a conserved and unconventional βTrCP recognition motif (DDAYPE) in the securin primary amino acid sequence of humans, nonhuman primates and rodents. Furthermore, downregulation of βTrCP caused an accumulation of securin in non-irradiated cells. We conclude that SCFβTrCP is the E3 ubiquitin ligase responsible for securin degradation after UV irradiation, and that it is involved in securin turnover in nonstressed cells.

SCF/β-TrCP Promotes Glycogen Synthase Kinase 3-Dependent Degradation of the Nrf2 Transcription Factor in a Keap1-Independent Manner

“…However, the mechanistic connection between GSK-3 and Nrf2 remains largely unexplored. A number of studies have demonstrated that GSK-3 directs the ubiquitination and proteasomal degradation of various transcription factors and other proteins by SCF/␤-TrCP; these include Snail (54), ␤-catenin (1,22,34), Gli2 and Gli3 (33,48), Xom (55), Cdc 25a (19), FGD1 and -3 (11,12), Mcl-1 (7), securin (24), prolactin receptor (46), and the phosphatase PHLPP1 (23). In these instances, GSK-3 phosphorylates a cluster of Ser/Thr residues in target proteins, which are then recognized by SCF/␤-TrCP.…”

Glycogen Synthase Kinase-3β (GSK3β) Negatively Regulates PTTG1/Human Securin Protein Stability, and GSK3β Inactivation Correlates with Securin Accumulation in Breast Tumors

“…We have reported that UV radiation induced the destruc- tion of securin that is mediated by SCF ␤TrCP ubiquitin ligase and prevented by GSK3 inhibitors, suggesting that this kinase plays a role in regulating securin levels following exposure of cells to DNA damage (15).…”

“…We previously reported that ultraviolet radiation-induced degradation of securin is mediated by SCF ␤TrCP (15). To know whether this E3 ubiquitin ligase is also responsible for securin degradation promoted by GSK3␤ phosphorylation in non-irradiated cells, a dominant-negative variant of ␤TrCP lacking the F-box domain was used (32).…”

“…We previously described the role of human securin in cell cycle arrest after UV irradiation, when it probably prevents cell proliferation during DNA damage repair (14). Irradiation causes rapid proteasomedependent securin degradation that is mediated by SCF ␤TrCP E3 ubiquitin ligase and prevented by inhibitors of GSK3 (15). A role for securin in cancer pathogenesis is supported by the observation of increased expression of securin in different tumors (16 -19) and in samples under a putative metastasis program (20).…”

A new layer of degradation mechanism for PR-Set7/Set8 during cell cycle

“…62 Interestingly, after exposure to UV irradiation, Securin is degraded by b-TRCP and results in cell cycle arrest. 63 Moreover, REST (repressor element-1-silencing transcription factor), which participates in cell cycle, is also degraded by b-TRCP. 64 In line with this observation, b-TRCP-mediated degradation of Claspin is important for the efficient and timely termination of the DNA replication checkpoint.…”