Biology subjects

Xiahou, Z.

Publications and source records attributed to Xiahou, Z..

2 recordsLinked to original sources

bioRxiv2022

PLK1 O-GlcNAcylation is essential for dividing mammalian cells and inhibits uterine carcinoma

The O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) mediates intracellular O-GlcNAcylation modification, whose function and substrates have entranced biologists and chemists alike. O-GlcNAcylation occurs on Ser/Thr residues and takes part in a vast array of physiological processes. OGT is essential for dividing mammalian cells, and it underscores many human diseases. Yet many of its fundamental substrates in the cell division process remains to be unveiled. Here we focus on its effect on Polo-like kinase 1 (PLK1), a mitotic master kinase that governs DNA replication, mitotic entry, chromosome segregation and mitotic exit. We found that PLK1 interacts with OGT and is O-GlcNAcylated. By utilizing stepped collisional energy/higher-energy collisional dissociation (sceHCD) mass spectrometry (MS) and mutagenesis studies, the critical O-GlcNAc site is located to be Thr291. Interestingly, T291N is a uterine carcinoma mutant in the TCGA database. Biochemical assays show that T291A and T291N both increase PLK1 stability. Using stable H2B-GFP cells, we show that PLK1-T291A and -T291N mutants display chromosome segregation defects, and result in misaligned and lagging chromosomes. In mouse xenograft models, we demonstrate that the O-GlcNAc-deficient PLK1-T291A and -T291N mutants would enhance uterine carcinoma in animals. Hence, we propose that OGT partially exerts its mitotic function through O-GlcNAcylation of PLK1, and sceHCD MS might be a new method to reveal many more O-GlcNAcylation substrates.

cancer biology↗

bioRxiv2019

MYPT1 O-GlcNAcylation Dictates Timely Disjunction of Centrosomes

The role of O-linked N-acetylglucosamine (O-GlcNAc) modification in the cell cycle has been enigmatic. Previously, both O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) disruption have been shown to derail the mitotic centrosome numbers, suggesting that mitotic O-GlcNAc oscillation needs to be in concert with mitotic progression to account for centrosome integrity. Here we attempted to address the underlying molecular mechanism by both chemical approaches and biological assays, and observed that Thiamet-G (OGA inhibitor) incubation strikingly elevated centrosomal distances, suggestive of premature centrosome disjuction. These aberrancies could be overcome by inhibiting Polo-like kinase 1 (Plk1), a mitotic master kinase. Plk1 inactivation is modulated by the Myosin Phosphatase Targeting Subunit 1 (MYPT1)-Protein Phosphatase 1 c{beta} (PP1c{beta}) complex. Interestingly, MYPT1 is abundantly O-GlcNAcylated and the modified residues have been detected in a recent O-GlcNAc profiling screen utilizing chemoenzymatic labeling and bioorthogonal conjugation. We demonstrate that MYPT1 is O-GlcNAcylated at T577, S585, S589 and S601, which antagonizes CDK1-dependent phosphorylation at S473, subsequently attenuating the association between MYPT1 and Plk1, and promoting PLK1 activity. Thus under high O-GlcNAc, Plk1 is untimely activated, conducive to inopportune centrosome separation and disrupting the cell cycle. We propose that too much O-GlcNAc is equally deleterious as too little O-GlcNAc, and a fine balance between the OGT/OGA duo is indispensible for successful mitotic divisions.

biochemistry↗