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Prm3p is a pheromone-induced peripheral nuclear envelope protein required for yeast nuclear fusion.

Nuclear membrane fusion is the last step in the mating pathway of the yeast Saccharomyces cerevisiae. We adapted a bioinformatics approach to identify putative pheromone-induced membrane proteins potentially required for nuclear membrane fusion. One protein, Prm3p, was found to be required for nuclear membrane fusion; disruption of PRM3 caused a strong bilateral defect, in which nuclear congression was completed but fusion did not occur. Prm3p was localized to the nuclear envelope in pheromone-responding cells, with significant colocalization with the spindle pole body in zygotes. A previous report, using a truncated protein, claimed that Prm3p is localized to the inner nuclear envelope. Based on biochemistry, immunoelectron microscopy and live cell microscopy, we find that functional Prm3p is a peripheral membrane protein exposed on the cytoplasmic face of the outer nuclear envelope. In support of this, mutations in a putative nuclear localization sequence had no effect on full-length protein function or localization. In contrast, point mutations and deletions in the highly conserved hydrophobic carboxy-terminal domain disrupted both protein function and localization. Genetic analysis, colocalization, and biochemical experiments indicate that Prm3p interacts directly with Kar5p, suggesting that nuclear membrane fusion is mediated by a protein complex.

Pubmed ID: 19297527


  • Shen S
  • Tobery CE
  • Rose MD


Molecular biology of the cell

Publication Data

May 1, 2009

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM-37739
  • Agency: NIGMS NIH HHS, Id: R01 GM037739
  • Agency: NIGMS NIH HHS, Id: R01 GM037739-22

Mesh Terms

  • Amino Acid Sequence
  • Conserved Sequence
  • Genes, Fungal
  • Hydrophobic and Hydrophilic Interactions
  • Membrane Fusion
  • Membrane Proteins
  • Molecular Sequence Data
  • Mutation
  • Nuclear Envelope
  • Nuclear Proteins
  • Pheromones
  • Protein Binding
  • Protein Stability
  • Protein Transport
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Spindle Apparatus