Immobility, inheritance and plasticity of shape of the yeast nucleus.
BACKGROUND
Since S. cerevisiae undergoes closed mitosis, the nuclear envelope of the daughter nucleus is continuous with that of the maternal nucleus at anaphase. Nevertheless, several constitutents of the maternal nucleus are not present in the daughter nucleus. The present study aims to identify proteins which impact the shape of the yeast nucleus and to learn whether modifications of shape are passed on to the next mitotic generation. The Esc1p protein of S. cerevisiae localizes to the periphery of the nucleoplasm, can anchor chromatin, and has been implicated in targeted silencing both at telomeres and at HMR.


RESULTS
Upon increased Esc1p expression, cell division continues and dramatic elaborations of the nuclear envelope extend into the cytoplasm. These "escapades" include nuclear pores and associate with the nucleolus, but exclude chromatin. Escapades are not inherited by daughter nuclei. This exclusion reflects their relative immobility, which we document in studies of prezygotes. Moreover, excess Esc1p affects the levels of multiple transcripts, not all of which originate at telomere-proximal loci. Unlike Esc1p and the colocalizing protein, Mlp1p, overexpression of selected proteins of the inner nuclear membrane is toxic.


CONCLUSIONS
Esc1p is the first non-membrane protein of the nuclear periphery which - like proteins of the nuclear lamina of higher eukaryotes - can modify the shape of the yeast nucleus. The elaborations of the nuclear envelope ("escapades") which appear upon induction of excess Esc1p are not inherited during mitotic growth. The lack of inheritance of such components could help sustain cell growth when parental nuclei have acquired potentially deleterious characteristics.
Hattier
Thomas
T
Cell Biology Program, Case Western Reserve University, 10700 Euclid Avenue, Cleveland, OH, 44106 USA. thattier@gmail.com
Andrulis
Erik D
ED
Tartakoff
Alan M
AM
D002467:Cell Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D022003:Cell Nucleus Structures / Q000648:ultrastructure; D003593:Cytoplasm / Q000648:ultrastructure; D007700:Kinetics; D008938:Mitosis; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism; D053140:Organelle Shape; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism / Q000648:ultrastructure
C495981:Esc1 protein, S cerevisiae; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins