Nep98p Is a Component of the Yeast Spindle Pole Body and Essential for Nuclear Division and Fusion

During the mating of yeast Saccharomyces cerevisiae , two haploid nuclei fuse to produce a diploid nucleus. This process requires the functions of BiP/Kar2p, a member of the Hsp70 family in the endoplasmic reticulum, and its partner protein, Jem1p. To investigate further the role of BiP and Jem1p in...

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Bibliographic Details
Published in:The Journal of biological chemistry 2003-03, Vol.278 (11), p.9938-9943
Main Authors: Nishikawa, Shuh-Ichi, Terazawa, Yumiko, Nakayama, Takeshi, Hirata, Aiko, Makio, Tadashi, Endo, Toshiya
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Cell Nucleus - metabolism
G2 Phase
Genes, Fungal
HSP70 Heat-Shock Proteins - metabolism
Membrane Proteins - chemistry
Membrane Proteins - metabolism
Membrane Proteins - physiology
Microscopy, Electron
Microscopy, Fluorescence
Mitosis
Molecular Chaperones
Molecular Sequence Data
Mutagenesis, Site-Directed
Mutation
Nuclear Proteins
Plasmids - metabolism
Protein Binding
Protein Structure, Tertiary
Saccharomyces cerevisiae - metabolism
Saccharomyces cerevisiae Proteins - chemistry
Saccharomyces cerevisiae Proteins - metabolism
Saccharomyces cerevisiae Proteins - physiology
Spindle Apparatus
Temperature
Two-Hybrid System Techniques
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Summary:During the mating of yeast Saccharomyces cerevisiae , two haploid nuclei fuse to produce a diploid nucleus. This process requires the functions of BiP/Kar2p, a member of the Hsp70 family in the endoplasmic reticulum, and its partner protein, Jem1p. To investigate further the role of BiP and Jem1p in nuclear fusion, we screened for partner proteins for Jem1p by the yeast two-hybrid system and identified Nep98p. Nep98p is an essential integral membrane protein of the nuclear envelope and is enriched in the spindle pole body (SPB), the sole microtubule-organizing center in yeast. Temperature-sensitive nep98 mutant cells contain abnormal SPBs lacking the half-bridge, suggesting the essential role of Nep98p in the organization of the normal SPB. Additionally, nep98 mutant cells show defects in mitotic nuclear division and nuclear fusion during mating. Because Jem1p is not required for nuclear division, Nep98p probably has dual functions in Jem1p-dependent karyogamy and in Jem1p-independent nuclear division.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M210934200