SUMOylation Promotes Nuclear Import and Stabilization of Polo-like Kinase 1 to Support Its Mitotic Function

Abstract

SUMMARY As a pivotal mitotic regulator, polo-like kinase 1 (PLK1) is under highly coordinated and multilayered regulation. However, the pathways that control PLK1’s activity and function have just begun to be elucidated. PLK1 has recently been shown to be functionally modulated by post-translational modifications (PTMs), including phosphorylation and ubiquitination. Herein, we report that a novel PTM, SUMOylation, plays an essential role in regulating PLK1’s mitotic function. We found that Ubc9 was recruited to PLK1, upon initial phosphorylation and activation by CDK1/cyclin B. By in vivo and in vitro SUMOylation assays, PLK1 was identified as a physiologically relevant SUMO-targeted protein, preferentially modified by SUMO-1. We further showed that K492 on PLK1 is essential for SUMOylation. SUMOylation causes PLK1’s nuclear import and significantly increases its protein stability, both of which are critical for normal mitotic progression and genomic integrity. Our findings suggest that SUMOylation is another important regulatory mechanism governing PLK1’s mitotic function.

SUMO-Mediated Regulation of Nuclear Functions and Signaling Processes

“…In particular, sumoylated lysines are abundantly found near CDK1 consensus sites, and sumoylation of these sequences showed dependence on CDK1. This finding is in line with previously reported phosphorylation-dependent sumoylation (Hietakangas et al, 2006) and the aforementioned ability of CdK1 to enhance SUMO E2 activity (Su et al, 2012; Wen et al, 2017). One outcome of CDK1-mediated SUMO E2 regulation is that phosphorylated E2 interacts with the Polo-kinase, leading to the latter’s SUMO1 conjugation.…”

“…In response to hypoxia, SUMO E2 acetylation reduces its interaction with sumoylation consensus sites, thus diminishing sumoylation of many proteins (Hsieh et al, 2013). On the other hand, SUMO E2 phosphorylation by CDK1/cyclin B during mitosis increases its overall activity toward forming thioester bonds with SUMO (Su et al, 2012; Wen et al, 2017). Finally, sumoylation of SUMO E2 favors SUMO chain formation in yeast and target discrimination in mammals (Klug et al, 2013; Knipscheer et al, 2008).…”

“…One outcome of CDK1-mediated SUMO E2 regulation is that phosphorylated E2 interacts with the Polo-kinase, leading to the latter’s SUMO1 conjugation. This in turn serves to promote Polo-kinase nuclear import and stabilization, driving mitotic progression (Wen et al, 2017). Such a kinase-SUMO E2-kinase regulatory relay has also been observed in other contexts (Fig 3B).…”

The methyltransferase SETD6 regulates Mitotic progression through PLK1 methylation

“…The kinase activity of PLK1 throughout the cell cycle is precisely orchestrated by the modulation of its stability, localization, conformation, and catalytic activity using posttranslation modifications (PTMs), including phosphorylation (5), dephosphorylation (7), ubiquitination (8), and recently shown sumoylation (9). During mitosis, PLK1 is phosphorylated by the Aurora A and B kinases on a threonine residue (Thr-210) positioned in its activation loop (T-loop), and this phosphorylation is required for its activity (5,10).…”

A polo-like kinase modulates cytokinesis and flagella biogenesis in Giardia lamblia

“…The nuclear localization signal (NLS) and destruction box (D-box) were not observed in the amino acid sequence of GlPLK, whereas PLK1 has canonical sequences for NLS and D-box [30]. Based on studies showing that PLK1 SUMOylation is involved in its nuclear localization [31,32], a putative SUMO interaction sequence and a target sequence for SUMO were found in GlPLK using a SUMOylation prediction program (GPS SUMP 1.0). The absence of D-box in cyclin B, AK, and PLK of G. lamblia indicates a regulatory mechanism other than ubiquitin-mediated degradation [33].…”