Abstract
Polo-like kinase 1 (Plk1) is a crucial cell cycle regulator by its specific localization and activity during cell cycle. It has been shown that the phosphorylation and ubiquitylation of Plk1 are required for its own activation and localization. Here, we report that SUMOylation regulates the activity of Plk1 in the lepidopteran insect of Bombyx mori. In the absence of SUMOylation, it causes the lost localization of Plk1 on centrosomes and kinetochores, as well as an uneven distribution in midzone. We further identify that the putative SUMOylation site of Bombyx Plk1 at lysine 466 is required for its localization on centrosomes, and K466 mutation in Plk1 could influence its interaction with Smt3/Ubc9 complex. These findings are also confirmed by Drosophila Polo and human Plk1, which together reveals a conserved role of Plk1 SUMOylation in mammals. Moreover, conjugation of Smt3 to Plk1 SUMOylation mutant promotes its localization on centrosomes and kinetochores, and rescues functional defects of chromosome alignment in cells depleted of endogenous Plk1. Altogether, the present data indicate that the SUMOylation of Plk1 could participate in proper chromosome alignment and segregation during mitosis, and provides a novel layer for the regulation of Plk1 localization and activity throughout cell cycle.
Highlights
Polo-like kinase 1 (Plk1), as a mitotic kinase, is one of the most important regulators for cell cycle progression in various eukaryotic organisms from yeast to mammals[1,2,3]
We identified BmPlk[1] as a substrate of the SUMOylation system in the silkworm Bombyx mori, which could interact with BmSmt3/BmUbc[9] complex to regulate the localizations of BmPlk[1] on centrosomes and kinetochores
To decipher the role of silkworm Plk[1], we carried out RNAi experiments in cultured silkworm cells by using two different double-stranded RNA (dsRNA) that target the gene body and 3′ untranslated region (UTR) of BmPLK1, respectively
Summary
Polo-like kinase 1 (Plk1), as a mitotic kinase, is one of the most important regulators for cell cycle progression in various eukaryotic organisms from yeast to mammals[1,2,3]. Consistent with the functions of Plk[1] in the cell cycle, expression of Plk[1] has been reported to be elevated in human cancers, which contributes to the formation and progression of tumors[7,8,9]. It has been recently reported that the ubiquitylation-dependent localization of Plk[1] in mitosis modulates its recruitment to kinetochores and regulates the faithful alignment and segregation of chromosomes[14] Another layer for Plk[1] regulation is its activation. The site of BmPlk[1] lysine 466 is much conserved with the human Plk[1] lysine 492 that has been confirmed as an ubiquitylation site All these data provides a very interesting crosstalk between ubiquitylation and SUMOylation on the same protein target, and gives a novel layer for the regulation of Plk[1] localization and activity mediated by the SUMOylation signaling during the cell cycle
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