Rpg1/Tif32p accumulates at sites of the localized growth.
Jiri Hasek, Katerina Malinska, Ivana Janatova
Cell and Mol. Microbiology, Inst.Microbiology ASCR, Videnska 1083,
Prague 4, 14220, Czech Republic
Rpg1/Tif32p is the essential subunit of the translation initiation
factor 3 core complex (eIF3) of Saccharomyces cerevisiae. We have
shown that Rpg1p is partially localized to microtubules and physically
interacts with the actin-associated protein Sla2/End4/Mop2. In this
work, we co-localized Rpg1p with Sla2p, Hcr1p and the endoplasmic
reticulum marker Elo3-GFP in wild type cells and sla2 deletion
mutants using the immunofluorescence microscopy. Proteins Hcr1, Sla2 and
Rpg1 were obviously co-localized at the tip of the emerging bud. In
comparison to wild type cells, the localization of Rpg1p to microtubules
seemed to be prominent in the sla2 deletion mutant. To monitor
distribution of Rpg1p in living cells, we prepared various C-terminal
Rpg1-GFP fusions. In general, living wild type cells expressing Rpg1-GFP
from the RPG1 promoter displayed almost homogeneous fluorescence
in the cytoplasm. Nevertheless, in some living cells we clearly observed
filamentous structures associated with patches of Rpg1-GFP near the bud
tip and the bud neck. These patches were dominant in cells overproducing
Rpg1-GFP. The accumulation of Rpg1-GFP near the tip of the emerging bud
was prominent in living cells of the cdc28-4 ts mutant shifted
back from 37°C to 25°C. We suggest that the accumulation of Rpg1p at
certain sites at the cell periphery is associated with the establishment
of the localized growth. This work was financed by grant GACR
204/02/1424 to JH.
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