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The mitochondrial histone HM: an evolutionary link between bacterial HU and nuclear HMG1 proteins
T L Megraw1, L R Kao, C B Chae
1Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill 27599-7260, USA.
Abstract:
The mitochondrial histone HM is a very abundant protein in yeast mitochondria that wraps DNA and activates transcription in vitro and is required within the cell for proper maintenance of the mitochondrial chromosome. HM and the bacterial histone-like protein HU have similar activities in vitro and can substitute for each other in E coli cells and in yeast mitochondria. HM also appears to be functionally homologous to nuclear HMG1 proteins, with which it shares a high degree of sequence homology. We report here the isolation of extragenic suppressors of the yeast HM mutant temperature-sensitive phenotype. We also examined the effects of the lack of HM protein and of respiration deficiency on yeast cells mutant for the NHP6 proteins, the putative yeast nuclear HMG1 homologues.
Insights
Yeast mitochondrial histone HM protein maintains mitochondrial DNA and activates transcription. Researchers identified suppressors of HM mutations and studied its relationship with nuclear HMG1 homologues (NHP6 proteins).
Area of Science:
- Mitochondrial biology
- Molecular genetics
- Yeast genetics
Background:
- Mitochondrial histone HM is abundant in yeast, essential for mitochondrial DNA maintenance and transcription.
- HM shares functional and sequence homology with bacterial HU and nuclear HMG1 proteins.
Purpose of the Study:
- To investigate the function of mitochondrial histone HM in yeast.
- To identify genetic interactions and functional relationships of HM with nuclear HMG1 homologues.
Main Methods:
- Isolation of extragenic suppressors of yeast HM mutant temperature-sensitive phenotype.
- Analysis of yeast cells lacking HM protein and exhibiting respiration deficiency.
- Examination of yeast cells mutant for NHP6 proteins, the putative nuclear HMG1 homologues.
Main Results:
- Identification of extragenic suppressors providing insights into HM function.
- Characterization of the effects of HM absence and respiration deficiency on NHP6 mutant cells.
- Demonstration of functional links between mitochondrial HM and nuclear NHP6 proteins.
Conclusions:
- Mitochondrial histone HM plays a critical role in yeast mitochondrial chromosome maintenance and transcription.
- Functional relationships exist between mitochondrial HM and nuclear HMG1 homologues (NHP6) in yeast.
- Further research is warranted to fully elucidate the interplay between mitochondrial and nuclear histone-like proteins.