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  • The EMBO Journal (1998) 17, 6449 - 6464
  • doi:10.1093/emboj/17.22.6449

A novel complex of membrane proteins required for formation of a spherical nucleus

Symeon Siniossoglou1,4, Helena Santos-Rosa1,4, Juri Rappsilber2, Mathias Mann3 and Ed Hurt1

  1. BZH, Biochemie-Zentrum Heidelberg, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany
  2. EMBL, Meyerhofstrasse1, D-69117 Heidelberg, Germany
  3. Center for Experimental Bioinformatics, Odense University, Odense, Denmark
  4. S.Siniossoglou and H.Santos-Rosa contributed equally to this work

Correspondence to:

Ed Hurt, E-mail: cg5@ix.urz.uni-heidelberg.de

Received 14 August 1998; Accepted 24 September 1998; Revised 23 September 1998

Two membrane proteins were identified through their genetic interaction with the nucleoporin Nup84p and shown to participate in nuclear envelope morphogenesis in yeast. One component is a known sporulation factor Spo7p, and the other, Nem1p, a novel protein whose C-terminal domain is conserved during eukaryotic evolution. Spo7p and Nem1p localize to the nuclear/ER membrane and behave biochemically as integral membrane proteins. Nem1p binds to Spo7p via its conserved C-terminal domain. Although cells without Spo7p or Nem1p are viable, they exhibit a drastically altered nuclear morphology with long, pore-containing double nuclear membrane extensions. These protrusions emanate from a core nucleus which contains the DNA, and penetrate deeply into the cytoplasm. Interestingly, not only Spo7- and Nem1-, but also several nucleoporin mutants are defective in sporulation. Thus, Spo7p and Nem1p, which exhibit a strong genetic link to nucleoporins of the Nup84p complex, fulfil an essential role in formation of a spherical nucleus and meiotic division.

  • Keywords:

    • membrane biogenesis,
    • nuclear envelope,
    • nuclear morphology,
    • nuclear pore complex,
    • sporulation