2. Academic Validation
  3. AKIRIN2 controls the nuclear import of proteasomes in vertebrates

AKIRIN2 controls the nuclear import of proteasomes in vertebrates

  • Nature. 2021 Nov;599(7885):491-496. doi: 10.1038/s41586-021-04035-8.
Melanie de Almeida  # 1 2,  Matthias Hinterndorfer  # 1 2,  Hanna Brunner 1 2,  Irina Grishkovskaya 1,  Kashish Singh 1 3,  Alexander Schleiffer 1,  Julian Jude 1 4,  Sumit Deswal 1 5,  Robert Kalis 1 2,  Milica Vunjak 2 6,  Thomas Lendl 1,  Richard Imre 1,  Elisabeth Roitinger 1,  Tobias Neumann 1 7,  Susanne Kandolf 1,  Michael Schutzbier 1,  Karl Mechtler 1,  Gijs A Versteeg 6,  David Haselbach 8,  Johannes Zuber 9 10
Affiliations

Affiliations

  • 1 Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria.
  • 2 Vienna BioCenter PhD Program, Doctoral School of the University at Vienna and Medical University of Vienna, Vienna BioCenter (VBC), Vienna, Austria.
  • 3 MRC Laboratory of Molecular Biology, Cambridge, UK.
  • 4 Twist Bioscience, San Francisco, CA, USA.
  • 5 Genome Engineering, Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden.
  • 6 Department of Microbiology, Immunobiology and Genetics, Max Perutz Labs, University of Vienna, Vienna BioCenter (VBC), Vienna, Austria.
  • 7 Quantro Therapeutics, Vienna, Austria.
  • 8 Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria. david.haselbach@imp.ac.at.
  • 9 Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria. johannes.zuber@imp.ac.at.
  • 10 Medical University of Vienna, Vienna BioCenter (VBC), Vienna, Austria. johannes.zuber@imp.ac.at.
  • # Contributed equally.
PMID: 34711951 DOI: 10.1038/s41586-021-04035-8
Abstract

Protein expression and turnover are controlled through a complex interplay of transcriptional, post-transcriptional and post-translational mechanisms to enable spatial and temporal regulation of cellular processes. To systematically elucidate such gene regulatory networks, we developed a CRISPR screening assay based on time-controlled Cas9 mutagenesis, intracellular immunostaining and fluorescence-activated cell sorting that enables the identification of regulatory factors independent of their effects on cellular fitness. We pioneered this approach by systematically probing the regulation of the transcription factor MYC, a master regulator of cell growth1-3. Our screens uncover a highly conserved protein, AKIRIN2, that is essentially required for nuclear protein degradation. We found that AKIRIN2 forms homodimers that directly bind to fully assembled 20S proteasomes to mediate their nuclear import. During mitosis, proteasomes are excluded from condensing chromatin and re-imported into newly formed daughter nuclei in a highly dynamic, AKIRIN2-dependent process. Cells undergoing mitosis in the absence of AKIRIN2 become devoid of nuclear proteasomes, rapidly causing accumulation of MYC and other nuclear proteins. Collectively, our study reveals a dedicated pathway controlling the nuclear import of proteasomes in vertebrates and establishes a scalable approach to decipher regulators in essential cellular processes.

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