Yeast nuclear envelope subdomains with distinct abilities to resist membrane expansion.
Little is known about what dictates the round shape of the yeast Saccharomyces cerevisiae nucleus. In spo7Delta mutants, the nucleus is misshapen, exhibiting a single protrusion. The Spo7 protein is part of a phosphatase complex that represses phospholipid biosynthesis. Here, we report that the nuclear protrusion of spo7Delta mutants colocalizes with the nucleolus, whereas the nuclear compartment containing the bulk of the DNA is unaffected. Using strains in which the nucleolus is not intimately associated with the nuclear envelope, we show that the single nuclear protrusion of spo7Delta mutants is not a result of nucleolar expansion, but rather a property of the nuclear membrane. We found that in spo7Delta mutants the peripheral endoplasmic reticulum (ER) membrane was also expanded. Because the nuclear membrane and the ER are contiguous, this finding indicates that in spo7Delta mutants all ER membranes, with the exception of the membrane surrounding the bulk of the DNA, undergo expansion. Our results suggest that the nuclear envelope has distinct domains that differ in their ability to resist membrane expansion in response to increased phospholipid biosynthesis. We further propose that in budding yeast there is a mechanism, or structure, that restricts nuclear membrane expansion around the bulk of the DNA.
The Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Joseph L
JL
Campbell
Alexander
A
Lorenz
Keren L
KL
Witkin
Thomas
T
Hays
Josef
J
Loidl
Orna
O
Cohen-Fix
D002466:Cell Nucleolus / Q000648:ultrastructure; D002467:Cell Nucleus / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure*; D015825:Chromosomes, Fungal / Q000648:ultrastructure; D004275:DNA, Ribosomal / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000648:ultrastructure; D017353:Gene Deletion; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009685:Nuclear Envelope / Q000235:genetics* / Q000648:ultrastructure*; D009687:Nuclear Proteins / Q000032:analysis / Q000378:metabolism; D010743:Phospholipids / Q000096:biosynthesis; D016601:RNA-Binding Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*
D004275:DNA, Ribosomal; C080988:MLP1 protein, S cerevisiae; D008565:Membrane Proteins; D009687:Nuclear Proteins; D010743:Phospholipids; D016601:RNA-Binding Proteins; C116365:SPO7 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins