Nuclear targeted Saccharomyces cerevisiae asparagine synthetases associate with the mitotic spindle regardless of their enzymatic activity

PLoS One. 2020 Dec 21;15(12):e0243742. doi: 10.1371/journal.pone.0243742. eCollection 2020.

Abstract

Recently, human asparagine synthetase has been found to be associated with the mitotic spindle. However, this event cannot be seen in yeast because yeast takes a different cell division process via closed mitosis (there is no nuclear envelope breakdown to allow the association between any cytosolic enzyme and mitotic spindle). To find out if yeast asparagine synthetase can also (but hiddenly) have this feature, the coding sequences of green fluorescent protein (GFP) and nuclear localization signal (NLS) were introduced downstream of ASN1 and ASN2, encoding asparagine synthetases Asn1p and Asn2p, respectively, in the yeast genome having mCherrry coding sequence downstream of TUB1 encoding alpha-tubulin, a building block of the mitotic spindle. The genomically engineered yeast strains showed co-localization of Asn1p-GFP-NLS (or Asn2p-GFP-NLS) and Tub1p-mCherry in dividing nuclei. In addition, an activity-disrupted mutation was introduced to ASN1 (or ASN2). The yeast mutants still exhibited co-localization between defective asparagine synthetase and mitotic spindle, indicating that the biochemical activity of asparagine synthetase is not required for its association with the mitotic spindle. Furthermore, nocodazole treatment was used to depolymerize the mitotic spindle, resulting in lack of association between the enzyme and the mitotic spindle. Although yeast cell division undergoes closed mitosis, preventing the association of its asparagine synthetase with the mitotic spindle, however, by using yeast constructs with re-localized Asn1/2p have suggested the moonlighting role of asparagine synthetase in cell division of higher eukaryotes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aspartate-Ammonia Ligase / genetics
  • Aspartate-Ammonia Ligase / metabolism*
  • Carbon-Nitrogen Ligases with Glutamine as Amide-N-Donor / genetics
  • Carbon-Nitrogen Ligases with Glutamine as Amide-N-Donor / metabolism*
  • Cell Nucleus / metabolism
  • Green Fluorescent Proteins / chemistry
  • Green Fluorescent Proteins / genetics
  • Intravital Microscopy / methods
  • Luminescent Agents / chemistry
  • Luminescent Proteins / chemistry
  • Luminescent Proteins / genetics
  • Microscopy, Fluorescence
  • Mitosis / physiology*
  • Molecular Imaging / methods
  • Red Fluorescent Protein
  • Saccharomyces cerevisiae / physiology*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Spindle Apparatus / metabolism*

Substances

  • ASN1 protein, S cerevisiae
  • Luminescent Agents
  • Luminescent Proteins
  • Saccharomyces cerevisiae Proteins
  • Tub1 protein, S cerevisiae
  • Green Fluorescent Proteins
  • ASN2 protein, S cerevisiae
  • Aspartate-Ammonia Ligase
  • Carbon-Nitrogen Ligases with Glutamine as Amide-N-Donor
  • asparagine synthetase (glutamine-hydrolyzing)

Grants and funding

This project was supported by (1) the Coordinating Center for Thai Government Science and Technology Scholarship Students (CSTS) – the National Science and Technology Development Agency (NSTDA), (2) the National Research Council of Thailand (NRCT) in association with Office of the Permanent Secretary, Ministry of Higher Education, Science, Research and Innovation (MHESI), (3) the Development and Promotion of Science and Technology Talents Project (DPST), and (4) Mahidol University (MU).