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Mol. Cell. Biol., Dec 1997, 6847-6858, Vol 17, No. 12
CJ Bonangelino, NL Catlett and LS Weisman
During cell division, the vacuole of Saccharomyces cerevisiae partitions
between mother and daughter cells. A portion of the parental vacuole
membrane moves into the bud, and ultimately membrane scission divides the
vacuole into two separate structures. Here we characterize two yeast
mutations causing defects in vacuole membrane scission, vac7- 1 and
vac14-1. A third mutant, afab1-2 strain, isolated in a nonrelated screen
(A. Yamamoto et al., Mol. Biol. Cell 6:525-539, 1995) shares the vacuolar
phenotypes of the vac7-1 and vac14-1 strains. Unlike the wild type, mutant
vacuoles are not multilobed structures; in many cases, a single vacuole
spans both the mother and bud, with a distinct gap in the mother-bud neck.
Thus, even where the membranes are closely opposed, vacuole fission is
arrested. Simply enlarging the vacuole does not produce this mutant
phenotype. An additional common phenotype of these mutants is a defect in
vacuole acidification; however, vacuole scission in most other vacuole
acidification mutants is normal. An alteration in vacuole membrane lipids
could account for both the vacuole membrane scission and acidification
defects. Because a directed screen has not identified additional class III
complementation groups, it is likely that all three genes are involved in a
similar process. Interestingly, FAB1, was previously shown to encode a
putative phosphatidylinositol-4-phosphate 5-kinase. Moreover,
overexpression of FAB1 suppresses the vac14-1 mutation, which suggests that
VAC14 and FAB1 act at a common step. VAC7 encodes a novel 128-kDa protein
that is localized at the vacuole membrane. This location of Vac7p is
consistent with its involvement in vacuole morphology and inheritance.
Copyright © 1997, American Society for Microbiology
Vac7p, a novel vacuolar protein, is required for normal vacuole inheritance and morphology
Department of Biochemistry, University of Iowa, Iowa City 52242, USA.
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