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J. Cell Biol.,
Volume 141, Number 5, June 1, 1998 1107-1119


* Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544; and SEC35 was identified in a novel screen for
temperature-sensitive mutants in the secretory pathway
of the yeast Saccharomyces cerevisiae (. Genetics. 142:393-406). At the restrictive temperature, the sec35-1 strain exhibits a transport block between the ER and the Golgi apparatus and accumulates
numerous vesicles. SEC35 encodes a novel cytosolic
protein of 32 kD, peripherally associated with membranes. The temperature-sensitive phenotype of sec35-1
is efficiently suppressed by YPT1, which encodes the rab-like GTPase required early in the secretory pathway, or by SLY1-20, which encodes a dominant form of
the ER to Golgi target -SNARE-associated protein
Sly1p. Weaker suppression is evident upon overexpression of genes encoding the vesicle-SNAREs SEC22,
BET1, or YKT6. The cold-sensitive lethality that results from deleting SEC35 is suppressed by YPT1 or
SLY1-20. These genetic relationships suggest that
Sec35p acts upstream of, or in conjunction with, Ypt1p
and Sly1p as was previously found for Uso1p. Using a
cell-free assay that measures distinct steps in vesicle
transport from the ER to the Golgi, we find Sec35p is
required for a vesicle docking stage catalyzed by
Uso1p. These genetic and biochemical results suggest
Sec35p acts with Uso1p to dock ER-derived vesicles to
the Golgi complex.
Department of Biochemistry,
Dartmouth Medical School, Hanover, New Hampshire 03755
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