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A single mutation in the 15S rRNA gene confers non sense suppressor activity and interacts with mRF1 the release
Ali Gargouri1, Catherine Macadré1, Jaga Lazowska1
1Centre de Génétique Moléculaire, Laboratoire propre du C.N.R.S associé à l'Université Pierre et Marie Curie. CNRS F-91198 Gif-sur-Yvette cedex, France.
Abstract:
We have determined the nucleotide sequence of the mim3-1 mitochondrial ribosomal suppressor, acting on ochre mitochondrial mutations and one frameshift mutation in Saccharomyces cerevisiae. The 15s rRNA suppressor gene contains a G633 to C transversion. Yeast mitochondrial G633 corresponds to G517 of the E.coli 15S rRNA, which is occupied by an invariant G in all known small rRNA sequences. Interestingly, this mutation has occurred at the same position as the known MSU1 mitochondrial suppressor which changes G633 to A. The suppressor mutation lies in a highly conserved region of the rRNA, known in E.coli as the 530-loop, interacting with the S4, S5 and S12 ribosomal proteins. We also show an interesting interaction between the mitochondrial mim3-1 and the nuclear nam3-1 suppressors, both of which have the same action spectrum on mitochondrial mutations: nam3-1 abolishes the suppressor effect when present with mim3-1 in the same haploid cell. We discuss these results in the light of the nature of Nam3, identified by 1 as the yeast mitochondrial translation release factor. A hypothetical mechanism of suppression by "ribosome shifting" is also discussed in view of the nature of mutations suppressed and not suppressed.
Insights
The mim3-1 mitochondrial ribosomal suppressor in yeast has a G633 to C mutation in 15S rRNA, affecting mitochondrial mutations. This suppressor interacts with the nuclear NAM3-1 suppressor, potentially via ribosome shifting.
Area of Science:
- Molecular Biology
- Genetics
- Yeast Genetics
Background:
- Mitochondrial ribosomal suppressors are crucial for understanding gene expression.
- The mim3-1 suppressor in Saccharomyces cerevisiae targets specific mitochondrial mutations.
- Ribosomal RNA (rRNA) mutations can alter protein synthesis.
Purpose of the Study:
- To determine the nucleotide sequence of the mim3-1 mitochondrial ribosomal suppressor.
- To investigate the interaction between mitochondrial and nuclear suppressors.
- To elucidate the mechanism of mitochondrial mutation suppression.
Main Methods:
- Nucleotide sequencing of the mim3-1 gene.
- Analysis of yeast mitochondrial mutations.
- Genetic interaction studies between mim3-1 and nam3-1.
Main Results:
- The mim3-1 suppressor gene has a G633 to C transversion in the 15S rRNA.
- This mutation occurs at a conserved position in the 530-loop, interacting with ribosomal proteins.
- The nuclear NAM3-1 suppressor abolishes the mim3-1 suppressor effect.
Conclusions:
- The mim3-1 mutation is located in a functionally important region of the mitochondrial 15S rRNA.
- An interaction exists between mitochondrial (mim3-1) and nuclear (nam3-1) suppressors, possibly involving the translation release factor Nam3.
- A ribosome shifting mechanism is proposed to explain the observed suppression patterns.