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

Vol. 20, Issue 17, 3773-3782, September 1, 2009

This Article Full Text Full Text (PDF) Supplemental Materials All Versions of this Article: E09-02-0163v1 20/17/3773    most recent 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 Google Scholar Google Scholar Articles by Melloy, P. Articles by Rose, M. D. Search for Related Content PubMed PubMed Citation Articles by Melloy, P. Articles by Rose, M. D.

Distinct Roles for Key Karyogamy Proteins during Yeast Nuclear Fusion

Patricia Melloy^*,, Shu Shen^*, Erin White, and Mark D. Rose^*

*Department of Molecular Biology, Princeton University, Princeton, NJ 08544; Department of Biological and Allied Health Sciences, Fairleigh Dickinson University, Madison, NJ 07940; and MCD Biology, University of Colorado, Boulder, CO 80309

Submitted February 27, 2009; Revised June 19, 2009; Accepted June 23, 2009
Monitoring Editor: Daniel J. Lew

InCytes from MBC

During yeast mating, cell fusion is followed by the congression and fusion of the two nuclei. Proteins required for nuclear fusion are found at the surface (Prm3p) and within the lumen (Kar2p, Kar5p, and Kar8p) of the nuclear envelope (NE). Electron tomography (ET) of zygotes revealed that mutations in these proteins block nuclear fusion with different morphologies, suggesting that they act in different steps of fusion. Specifically, prm3 zygotes were blocked before formation of membrane bridges, whereas kar2, kar5, and kar8 zygotes frequently contained them. Membrane bridges were significantly larger and occurred more frequently in kar2 and kar8, than in kar5 mutant zygotes. The kinetics of NE fusion in prm3, kar5, and kar8 mutants, measured by live-cell fluorescence microscopy, were well correlated with the size and frequency of bridges observed by ET. However the kar2 mutant was defective for transfer of NE lumenal GFP, but not diffusion within the lumen, suggesting that transfer was blocked at the NE fusion junction. These observations suggest that Prm3p acts before initiation of outer NE fusion, Kar5p may help dilation of the initial fusion pore, and Kar2p and Kar8p act after outer NE fusion, during inner NE fusion.

Address correspondence to: Mark D. Rose (mdrose{at}princeton.edu)

Abbreviations used: NE, nuclear envelope; ET, electron tomography.