|
||
J. Cell Biol.,
Volume 145, Number 6, June 14, 1999 1153-1163
Instituto de Microbiología Bioquímica, Consejo Superior de Investigaciones Científicas/Universidad de Salamanca and
Departamento de Microbiología y Genética, Universidad de Salamanca 37007 Salamanca, Spain
The Saccharomyces cerevisiae CHS7 gene
encodes an integral membrane protein located in the
ER which is directly involved in chitin synthesis
through the regulation of chitin synthase III (CSIII)
activity. In the absence of CHS7 product, Chs3p, but
not other secreted proteins, is retained in the ER, leading to a severe defect in CSIII activity and consequently, to a reduced rate of chitin synthesis. In addition, chs7 null mutants show the yeast phenotypes
associated with a lack of chitin: reduced mating efficiency and lack of the chitosan ascospore layer, clear indications of Chs7p function throughout the S. cerevisiae
biological cycle.
CHS3 overexpression does not lead to increased levels of CSIII because the Chs3p excess is retained in the
ER. However, joint overexpression of CHS3 and CHS7
increases the export of Chs3p from the ER and this is
accompanied by a concomitant increase in CSIII activity, indicating that the amount of Chs7p is a limiting factor for CSIII activity. Accordingly, CHS7 transcription
is increased when elevated amounts of chitin synthesis
are detected.
These results show that Chs7p forms part of a new
mechanism specifically involved in Chs3p export from
the ER and consequently, in the regulation of CSIII activity.
This article has been cited by other articles:
|
|