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The nuclear Kluyveromyces lactis MRF1 gene encodes a mitochondrial class I peptide chain release factor that is
H J Pel1, S Rozenfeld, M Bolotin-Fukuhara
1Laboratoire de Génétique Moléculaire, Université Paris-Sud, Bâtiment 400, F-91405 Orsay, France.
Abstract:
We report the isolation and characterization of the Kluyveromyces lactis MRF1 gene encoding mitochondrial peptide chain release factor mRF-1. Over-expression of the KlMRF1 gene has a strong antisuppressive effect in a Saccharomyces cerevisiae mitochondrial nonsense suppressor strain. Inactivation of KlMRF1 results in a dual phenotype: most cells die after about 10-13 generations, while a small number of cells exceed this limit. We propose that the lethality is related to a loss of mitochondrial genome integrity. Surviving Klmrf1 cells are able to grow slowly on the non-fermentable substrate glycerol, indicating the existence of a second mitochondrial release factor activity. Our previous comparative analysis of class I release factors is refined by the incorporation of KlmRF-1 and ten recently identified prokaryotic release factor sequences.Keywords Kluyveromyces lactis middle dot Mitochondrial release factor middle dot MRF1 middle dot Peptide chain termination
Insights
We isolated and characterized the Kluyveromyces lactis MRF1 gene, crucial for mitochondrial peptide release. Its inactivation causes cell death, suggesting a role in maintaining mitochondrial genome integrity.
Area of Science:
- Molecular Biology
- Mitochondrial Genetics
- Yeast Biology
Background:
- Mitochondrial peptide chain release factors (mRFs) are essential for protein synthesis termination.
- Understanding the diversity and function of mRFs across different species is crucial for comprehending mitochondrial gene expression.
Purpose of the Study:
- To isolate and characterize the MRF1 gene from Kluyveromyces lactis.
- To investigate the function of the Kluyveromyces lactis mitochondrial release factor (KlMRF1) in vivo.
- To refine comparative analyses of class I release factors.
Main Methods:
- Gene isolation and characterization in Kluyveromyces lactis.
- Over-expression studies in Saccharomyces cerevisiae mitochondrial nonsense suppressor strains.
- Gene inactivation and phenotypic analysis in Kluyveromyces lactis.
- Comparative sequence analysis of release factors.
Main Results:
- The Kluyveromyces lactis MRF1 gene encodes mitochondrial peptide chain release factor mRF-1.
- Over-expression of KlMRF1 exhibits a strong antisuppressive effect in a Saccharomyces cerevisiae strain.
- Inactivation of KlMRF1 leads to cell lethality within 10-13 generations, linked to mitochondrial genome integrity loss.
- A small proportion of Klmrf1 cells survive and exhibit slow growth on glycerol, indicating a second mitochondrial release factor activity.
Conclusions:
- Kluyveromyces lactis MRF1 is essential for cell viability, likely due to its role in mitochondrial genome stability.
- The existence of a second mitochondrial release factor activity in Kluyveromyces lactis is suggested.
- The study refines comparative analyses of class I release factors with new sequence data.