2. Academic Validation
  3. Phosphorylation of SAF-A/hnRNP-U Serine 59 by Polo-Like Kinase 1 Is Required for Mitosis

Phosphorylation of SAF-A/hnRNP-U Serine 59 by Polo-Like Kinase 1 Is Required for Mitosis

  • Mol Cell Biol. 2015 Aug;35(15):2699-713. doi: 10.1128/MCB.01312-14.
Pauline Douglas 1,  Ruiqiong Ye 1,  Nicholas Morrice 2,  Sébastien Britton 3,  Laura Trinkle-Mulcahy 4,  Susan P Lees-Miller 5
Affiliations

Affiliations

  • 1 Departments of Biochemistry & Molecular Biology and Oncology, Robson DNA Science Centre, Southern Alberta Cancer Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
  • 2 Beatson Institute for Cancer Research, Glasgow, Scotland, United Kingdom.
  • 3 Institut de Pharmacologie et de Biologie Structurale, Centre National de la Recherche Scientifique, Université de Toulouse-Université Paul Sabatier, Equipe Labellisée Ligue contre le Cancer, Toulouse, France.
  • 4 Department of Cellular & Molecular Medicine and Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario, Canada.
  • 5 Departments of Biochemistry & Molecular Biology and Oncology, Robson DNA Science Centre, Southern Alberta Cancer Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada leesmill@ucalgary.ca.
PMID: 25986610 DOI: 10.1128/MCB.01312-14
Abstract

Scaffold attachment factor A (SAF-A), also called heterogenous nuclear ribonuclear protein U (hnRNP-U), is phosphorylated on serine 59 by the DNA-dependent protein kinase (DNA-PK) in response to DNA damage. Since SAF-A, DNA-PK catalytic subunit (DNA-PKcs), and protein Phosphatase 6 (PP6), which interacts with DNA-PKcs, have all been shown to have roles in mitosis, we asked whether DNA-PKcs phosphorylates SAF-A in mitosis. We show that SAF-A is phosphorylated on serine 59 in mitosis, that phosphorylation requires polo-like kinase 1 (PLK1) rather than DNA-PKcs, that SAF-A interacts with PLK1 in nocodazole-treated cells, and that serine 59 is dephosphorylated by protein Phosphatase 2A (PP2A) in mitosis. Moreover, cells expressing SAF-A in which serine 59 is mutated to alanine have multiple characteristics of aberrant mitoses, including misaligned chromosomes, lagging chromosomes, polylobed nuclei, and delayed passage through mitosis. Our findings identify serine 59 of SAF-A as a new target of both PLK1 and PP2A in mitosis and reveal that both phosphorylation and dephosphorylation of SAF-A serine 59 by PLK1 and PP2A, respectively, are required for accurate and timely exit from mitosis.

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