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Mol Cell Biol, May 1998, p. 2789-2803, Vol. 18, No. 5
Department of Cell Biology and Anatomy,
University of Alberta, Edmonton, Alberta T6G 2H7, Canada
Received 23 September 1997/Returned for modification 21 November
1997/Accepted 26 February 1998
Mutations in the SEC238 and SRP54 genes of
the yeast Yarrowia lipolytica not only cause
temperature-sensitive defects in the exit of the precursor form
of alkaline extracellular protease and of other secretory
proteins from the endoplasmic reticulum and in protein secretion
but also lead to temperature-sensitive growth in oleic acid-containing
medium, the metabolism of which requires the assembly of functionally
intact peroxisomes. The sec238A and
srp54KO mutations at the restrictive temperature
significantly reduce the size and number of peroxisomes,
affect the import of peroxisomal matrix and membrane proteins into the
organelle, and significantly delay, but do not prevent, the exit of
two peroxisomal membrane proteins, Pex2p and Pex16p, from the
endoplasmic reticulum en route to the peroxisomal membrane. Mutations
in the PEX1 and PEX6 genes, which encode
members of the AAA family of N-ethylmaleimide-sensitive fusion protein-like ATPases, not only affect the exit of precursor forms of secretory proteins from the endoplasmic reticulum but also
prevent the exit of the peroxisomal membrane proteins Pex2p and Pex16p
from the endoplasmic reticulum and cause the
accumulation of an extensive network of endoplasmic
reticulum membranes. None of the peroxisomal matrix proteins tested
associated with the endoplasmic reticulum in sec238A,
srp54KO, pex1-1, and pex6KO mutant
cells. Our data provide evidence that the endoplasmic reticulum is
required for peroxisome biogenesis and suggest that in
Y. lipolytica, the trafficking of some membrane
proteins, but not matrix proteins, to the peroxisome
occurs via the endoplasmic reticulum, results in their
glycosylation within the lumen of the endoplasmic
reticulum, does not involve transport through the Golgi, and requires
the products encoded by the SEC238, SRP54,
PEX1, and PEX6 genes.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Mutants of the Yeast Yarrowia lipolytica
Defective in Protein Exit from the Endoplasmic Reticulum Are Also
Defective in Peroxisome Biogenesis
*
Corresponding author. Mailing address: Department of
Cell Biology and Anatomy, University of Alberta, Medical Sciences
Building 5-14, Edmonton, Alberta T6G 2H7, Canada. Phone: (403)
492-9868. Fax: (403) 492-9278. E-mail:
rrachubi{at}anat.med.ualberta.ca.
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