Selective Induction of Mitochondrial Chaperones in Response to Loss of the Mitochondrial Genome

Molecular chaperones are known to play key roles in the synthesis, transport and folding of nuclear‐encoded mitochondrial proteins and of proteins encoded by mitochondrial DNA. Although the regulation of heat‐shock genes has been the subject of considerable investigation, regulation of the genes enc...

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Published in:	European journal of biochemistry Vol. 240; no. 1; pp. 98 - 103
Main Authors:	Martinus, Ryan D., Garth, Graeme P., Webster, Tracie L., Cartwright, Peter, Naylor, Dean J., Høj, Peter B., Hoogenraad, Nicholas J.
Format:	Journal Article
Language:	English
Published:	Oxford, UK Blackwell Publishing Ltd 01-08-1996
Subjects:	Animals Blotting, Western Cell Nucleus - metabolism Clone Cells Cytosol - metabolism DNA, Mitochondrial - drug effects DNA, Mitochondrial - genetics DNA, Mitochondrial - metabolism DNA, Neoplasm - drug effects DNA, Neoplasm - genetics DNA, Neoplasm - metabolism Ethidium - pharmacology Fluorescent Antibody Technique, Indirect gene activation heat shock Heat-Shock Proteins - biosynthesis Hot Temperature HSP70 Heat-Shock Proteins - biosynthesis HSP72 Heat-Shock Proteins Liver Neoplasms, Experimental mitochondria Mitochondria - drug effects Mitochondria - metabolism molecular chaperone Molecular Chaperones - biosynthesis Polymerase Chain Reaction Pyruvic Acid - pharmacology Rats stress response Transcription, Genetic Uridine - metabolism Uridine - pharmacology
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Summary:	Molecular chaperones are known to play key roles in the synthesis, transport and folding of nuclear‐encoded mitochondrial proteins and of proteins encoded by mitochondrial DNA. Although the regulation of heat‐shock genes has been the subject of considerable investigation, regulation of the genes encoding mitochondrial chaperones is not well defined. We have found that stress applied specifically to the mitochondria of mammalian cells is capable of eliciting an organelle‐specific, molecular chaperone response. Using the loss of mitochondrial DNA as a means of producing a specific mitochondrial stress, we show by Western‐blot analysis that mtDNA‐less (ϱ0) rat hepatoma cells show an increase in the steady‐state levels of chaperonin 60 (cpn 60) and chaperonin 10 (cpn 10). Nuclear transcription assays show that the upregulation of these chaperones is due to transcriptional activation. There was no effect on the inducible cytosolic Hsp 70, Hsp 72, nor on mtHsp 70 in ϱ0 cells, leading us to concluded that stress applied selectively to mitochondria elicits a specific molecular chaperone response. Heat stress was able to provide an additional induction of cpn 60 and cpn 10 above that obtained for the ϱ0 state alone, indicating that these genes have separate regulatory elements for the specific mitochondrial and general stress responses. Since the mitochondrial‐specific chaperones are encoded by nuclear DNA, there must be a mechanism for molecular communication between the mitochondrion and nucleus and this system can address how stress is communicated between these organelles.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0014-2956 1432-1033
DOI:	10.1111/j.1432-1033.1996.0098h.x