Nucleus-vacuole junctions in Saccharomyces cerevisiae are formed through the direct interaction of Vac8p with Nvj1p

Xiaozhou Pan, Paul Roberts, Yan Chen, Erik Kvam, Natalyia Shulga, Kristen Huang, Sandra Lemmon, David S. Goldfarb

Research output: Contribution to journalArticle

182 Scopus citations

Abstract

Vac8p is a vacuolar membrane protein that is required for efficient vacuole inheritance and fusion, cytosol-to-vacuole targeting, and sporulation. By analogy to other armadillo domain proteins, including β- catenin and importin α, we hypothesize that Vac8p docks various factors at the vacuole membrane. Two-hybrid and copurification assays demonstrated that Vac8p does form complexes with multiple binding partners, including Apg13p, Vab2p, and Nvj1p. Here we describe the surprising role of Vac8p-Nvj1p complexes in the formation of nucleus-vacuole (NV) junctions. Nvj1p is an integral membrane protein of the nuclear envelope and interacts with Vac8p in the cytosol through its C-terminal 40-60 amino acids (aa). Nvj1p green fluorescent protein (GFP) concentrated in small patches or rafts at sites of close contact between the nucleus and one or more vacuoles. Previously, we showed that Vac8p-GFP concentrated in intervacuole rafts, where is it likely to facilities vacuole-vacuole fusion, and in 'orphan' rafts at the edges of vacuole clusters. Orphan rafts of Vac8p red-sifted GFP (YFP) colocalize at sites of NV junctions with Nvj1p blue-sifted GFP (CFP). GFP-tagged nuclear pore complexes (NPCs) were excluded from NV junctions. In vac8-Δ cells, Nvj1p-GFP generally failed to concentrate into rafts and, instead, encircled the nucleus. NV junctions were absent in both nvj1-Δ and vac8-Δ cells. Overexpression of Nvj1p caused the profound proliferation of NV junctions. We conclude that Vac8p and Nvj1p are necessary components of a novel interoganelle junction apparatus.

Original languageEnglish (US)
Pages (from-to)2445-2457
Number of pages13
JournalMolecular biology of the cell
Volume11
Issue number7
DOIs
StatePublished - Jul 2000
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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