The Journal of Biochemistry
Online ISSN : 1756-2651
Print ISSN : 0021-924X
Misfolded Membrane-Bound Cytochrome P 450 Activates KAR2 Induction through Two Distinct Mechanisms
Thomas ZimmerAtsushi OguraAkinori OhtaMasamichi Takagi
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JOURNAL FREE ACCESS

1999 Volume 126 Issue 6 Pages 1080-1089

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Abstract

Using the mRNA differential display technique and Western blot analysis, the present study demonstrates that induction of KAR2 occurs when misfolded membrane-bound cytochrome P 450, mutated in its cytosolically exposed domain, is expressed in Saccharonzyces cerevisiae. Using various KAR2 promoter constructs in front of the Escherichia coli β-galactosidase reporter gene, we found a fast and strong induction through the heat shock element (HSE), which was enhanced several fold by its adjacent GC-rich region. Additionally, a less pronounced induction was detected for the UPR element (UPRE). As expected, this response was absent in the irel disruptant strain. However, the HSE-mediated induction was enhanced upon disruption of IRE1 suggesting that the HSE pathway can compensate for the lack of a functional UPR pathway. Western blotting confirmed that Kar2p levels were increased to the same extent in the irel disruptant and in the non-disruptant strain. Removal of the P 450 membrane-spanning region also abolished the UPRE-mediated induction of KAR2 transcription, but the HSE-mediated response remained. The data show for the first time that the transcription of KAR2 is significantly induced in response to a misfolded membrane-bound endoplasmic reticulum protein, and identifies the HSE and UPRE regions as KAR2 promoter elements responding to the misfolded cytosolic P 450 domain and to the membrane-integrated mutant P 450, respectively.

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© The Japanese Biochemical Society
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