2. Academic Validation
  3. Nuclear export of ubiquitinated proteins via the UBIN-POST system

Nuclear export of ubiquitinated proteins via the UBIN-POST system

  • Proc Natl Acad Sci U S A. 2018 May 1;115(18):E4199-E4208. doi: 10.1073/pnas.1711017115.
Shoshiro Hirayama 1,  Munechika Sugihara 2,  Daisuke Morito 3 4,  Shun-Ichiro Iemura 5,  Tohru Natsume 5,  Shigeo Murata 6,  Kazuhiro Nagata 7 3 4
Affiliations

Affiliations

  • 1 Laboratory of Protein Metabolism, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, 113-0033, Japan; s.hirayama@mol.f.u-tokyo.ac.jp nagata@cc.kyoto-su.ac.jp.
  • 2 Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, 603-8555, Japan.
  • 3 Institute for Protein Dynamics, Kyoto Sangyo University, Kyoto, 603-8555, Japan.
  • 4 Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency, Saitama, 332-0012, Japan.
  • 5 Biomedicinal Information Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo, 135-0064, Japan.
  • 6 Laboratory of Protein Metabolism, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, 113-0033, Japan.
  • 7 Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, 603-8555, Japan; s.hirayama@mol.f.u-tokyo.ac.jp nagata@cc.kyoto-su.ac.jp.
PMID: 29666234 DOI: 10.1073/pnas.1711017115
Abstract

Although mechanisms for protein homeostasis in the cytosol have been studied extensively, those in the nucleus remain largely unknown. Here, we identified that a protein complex mediates export of polyubiquitinated proteins from the nucleus to the cytosol. UBIN, a ubiquitin-associated (UBA) domain-containing protein, shuttled between the nucleus and the cytosol in a CRM1-dependent manner, despite the lack of intrinsic nuclear export signal (NES). Instead, the UBIN binding protein polyubiquitinated substrate transporter (POST) harboring an NES shuttled UBIN through nuclear pores. UBIN bound to polyubiquitin chain through its UBA domain, and the UBIN-POST complex exported them from the nucleus to the cytosol. Ubiquitinated proteins accumulated in the cytosol in response to Proteasome inhibition, whereas cotreatment with CRM1 Inhibitor led to their accumulation in the nucleus. Our results suggest that ubiquitinated proteins are exported from the nucleus to the cytosol in the UBIN-POST complex-dependent manner for the maintenance of nuclear protein homeostasis.

Keywords

protein aggregation; protein quality control; protein transport; ubiquitin.

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