QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Brizzio, V. Articles by Rose, M. D. Search for Related Content PubMed PubMed Citation Articles by Brizzio, V. Articles by Rose, M. D.

Vol. 10, Issue 3, 609-626, March 1999

Genetic Interactions between KAR7/SEC71, KAR8/JEM1, KAR5, and KAR2 during Nuclear Fusion in Saccharomyces cerevisiae

Valeria Brizzio,^* Waheeda Khalfan,^* Don Huddler,^* Christopher T. Beh,^* Søren S.L. Andersen,^*§ Martin Latterich, and Mark D. Rose^*¶

 ^*Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544-1014; and  Molecular Biology and Virology Laboratory, The Salk Institute, La Jolla, California 92037-109

During mating of Saccharomyces cerevisiae, two nuclei fuse to produce a single diploid nucleus. Two genes, KAR7 and KAR8, were previously identified by mutations that cause defects in nuclear membrane fusion. KAR7 is allelic to SEC71, a gene involved in protein translocation into the endoplasmic reticulum. Two other translocation mutants, sec63-1 and sec72, also exhibited moderate karyogamy defects. Membranes from kar7/sec71 and sec72, but not sec63-1, exhibited reduced membrane fusion in vitro, but only at elevated temperatures. Genetic interactions between kar7 and kar5 mutations were suggestive of protein-protein interactions. Moreover, in sec71 mutants, Kar5p was absent from the SPB and was not detected by Western blot or immunoprecipitation of pulse-labeled protein. KAR8 is allelic to JEMI, encoding an endoplasmic reticulum resident DnaJ protein required for nuclear fusion. Overexpression of KAR8/JEM1 (but not SEC63) strongly suppressed the mating defect of kar2-1, suggesting that Kar2p interacts with Kar8/Jem1p for nuclear fusion. Electron microscopy analysis of kar8 mutant zygotes revealed a nuclear fusion defect different from kar2, kar5, and kar7/sec71 mutants. Analysis of double mutants suggested that Kar5p acts before Kar8/Jem1p. We propose the existence of a nuclear envelope fusion chaperone complex in which Kar2p, Kar5p, and Kar8/Jem1p are key components and Sec71p and Sec72p play auxiliary roles.

---

   Present addresses: Millennium Pharmaceuticals, Cambridge, MA 02139; Department of Molecular and Cellular Biology, University of California, Berkeley, CA 94720; and ^§Department of Neurobiology, University of California at San Diego, La Jolla, CA 92093-0357.
^¶   Corresponding author. E-mail address: mrose{at}molbio.princeton.edu.

---

Molecular Biology of the Cell
Vol. 10, 609-626, March 1999
Copyright © 1999 by The American Society for Cell Biology

This article has been cited by other articles:

				P. Melloy, S. Shen, E. White, J. R. McIntosh, and M. D. Rose Nuclear fusion during yeast mating occurs by a three-step pathway J. Cell Biol., November 19, 2007; 179(4): 659 - 670. [Abstract] [Full Text] [PDF]

				M. F. Portereiko, L. Sandaklie-Nikolova, A. Lloyd, C. A. Dever, D. Otsuga, and G. N. Drews NUCLEAR FUSION DEFECTIVE1 Encodes the Arabidopsis RPL21M Protein and Is Required for Karyogamy during Female Gametophyte Development and Fertilization Plant Physiology, July 1, 2006; 141(3): 957 - 965. [Abstract] [Full Text] [PDF]

				D. Poteryaev, J. M. Squirrell, J. M. Campbell, J. G. White, and A. Spang Involvement of the Actin Cytoskeleton and Homotypic Membrane Fusion in ER Dynamics in Caenorhabditis elegans Mol. Biol. Cell, May 1, 2005; 16(5): 2139 - 2153. [Abstract] [Full Text] [PDF]

				B. Kroczynska, C. M. Evangelista, S. S. Samant, E. C. Elguindi, and S. Y. Blond The SANT2 Domain of the Murine Tumor Cell DnaJ-like Protein 1 Human Homologue Interacts with {alpha}1-Antichymotrypsin and Kinetically Interferes with Its Serpin Inhibitory Activity J. Biol. Chem., March 19, 2004; 279(12): 11432 - 11443. [Abstract] [Full Text] [PDF]

				S.-i. Nishikawa, Y. Terazawa, T. Nakayama, A. Hirata, T. Makio, and T. Endo Nep98p Is a Component of the Yeast Spindle Pole Body and Essential for Nuclear Division and Fusion J. Biol. Chem., March 7, 2003; 278(11): 9938 - 9943. [Abstract] [Full Text] [PDF]

				C. A. Christensen, S. W. Gorsich, R. H. Brown, L. G. Jones, J. Brown, J. M. Shaw, and G. N. Drews Mitochondrial GFA2 Is Required for Synergid Cell Death in Arabidopsis PLANT CELL, September 1, 2002; 14(9): 2215 - 2232. [Abstract] [Full Text] [PDF]

				A. Matynia, S. S. Salus, and S. Sazer Three proteins required for early steps in the protein secretory pathway also affect nuclear envelope structure and cell cycle progression in fission yeast J. Cell Sci., January 15, 2002; 115(2): 421 - 431. [Abstract] [Full Text] [PDF]

				S.-i. Nishikawa, S. W. Fewell, Y. Kato, J. L. Brodsky, and T. Endo Molecular Chaperones in the Yeast Endoplasmic Reticulum Maintain the Solubility of Proteins for Retrotranslocation and Degradation J. Cell Biol., May 29, 2001; 153(5): 1061 - 1070. [Abstract] [Full Text] [PDF]

				S. Wittke, M. Dünnwald, and N. Johnsson Sec62p, A Component of the Endoplasmic Reticulum Protein Translocation Machinery, Contains Multiple Binding Sites for the Sec-Complex Mol. Biol. Cell, November 1, 2000; 11(11): 3859 - 3871. [Abstract] [Full Text]

				A.-L. Hänninen, M. Simola, N. Saris, and M. Makarow The Cytoplasmic Chaperone Hsp104 Is Required for Conformational Repair of Heat-denatured Proteins in the Yeast Endoplasmic Reticulum Mol. Biol. Cell, November 1, 1999; 10(11): 3623 - 3632. [Abstract] [Full Text]

				M. Yu, R. H. A. Haslam, and D. B. Haslam HEDJ, an Hsp40 Co-chaperone Localized to the Endoplasmic Reticulum of Human Cells J. Biol. Chem., August 4, 2000; 275(32): 24984 - 24992. [Abstract] [Full Text] [PDF]