You are here: Vale Lab Home Page>Research>Other Projects>RNA Transport>mRNA Localization in Yeast>Creating Separate Plasma Membrane Compartments
Our discovery of the localized Ist2 mRNA through microarray technology led us down an unexpected path and into an unexplored area of yeast cell biology. By generating an Ist2-GFP fusion protein, we showed that Ist2 protein was localized in the plasma membrane of the incipient daughter as the result of localization of its protein to the bud tip. Surprisingly, the Ist2-GFP fluorescence was evenly distributed throughout the bud but then abruptly decreased at the mother-bud neck. The inability of Ist2-GFP to enter the mother was not due to an immobilization of the protein, since photobleaching experiments showed Ist2-GFP could rapidly diffuse in the plane of the membrane. Instead, the mother-bud segregation of Ist2p relied upon a diffusion barrier at the neck that required septin proteins. This was shown most clearly with a temperature-dependent septin mutant (cdc12-6): after the shift to the restrictive temperature and disassembly of the septin ring, Ist2-GFP could rapidly diffuse into the mother. These findings indicated that yeast has a specialized cytoskeletal structure at the neck that creates separate membrane compartments in the mother cell and the bud. Diffusion barriers have been described in higher eukaryotes but are poorly understood (e.g. between the cell body and axon in neurons and between different segments of sperm). These findings show that yeast can be used as a model system to study how distinct membrane compartments can be created and maintained.
|
Fig 1 - Ist2-GFP localization in wt and ts septin mutant cells. These experiments show that septins create distinct membrane compartments in the mother and the bud. (Click on an image for a larger view) |
|
Fig 2 - Ist2p is localized through mRNA transport and a physical barrier to diffusion at the mother-bud neck. (Click on an image for a larger view) |
updated 4/9/07
back to Home Page
