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

• Published in: The Journal of biological chemistry Vol. 278; no. 11; pp. 9938 - 9943
• Main Authors: Nishikawa, Shuh-Ichi, Terazawa, Yumiko, Nakayama, Takeshi, Hirata, Aiko, Makio, Tadashi, Endo, Toshiya
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 14.03.2003
• 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
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M210934200

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.