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Loss of the mitochondrial protein-only ribonuclease P complex causes aberrant tRNA processing and lethality in
Aditya Sen1, Agnes Karasik1, Aranganathan Shanmuganathan1
1Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, MD, 20814, USA.
Abstract:
Proteins encoded by mitochondrial DNA are translated using mitochondrially encoded tRNAs and rRNAs. As with nuclear encoded tRNAs, mitochondrial tRNAs must be processed to become fully functional. The mitochondrial form of ribonuclease P (mt:RNase P) is responsible for 5'-end maturation and is comprised of three proteins; mitochondrial RNase P protein (MRPP) 1 and 2 together with proteinaceous RNase P (PRORP). However, its mechanism and impact on development is not yet known. Using homology searches, we have identified the three proteins composing Drosophila mt:RNase P: Mulder (PRORP), Scully (MRPP2) and Roswell (MRPP1). Here, we show that each protein is essential and localizes with mitochondria. Furthermore, reducing levels of each causes mitochondrial deficits, which appear to be due at least in part to defective mitochondrial tRNA processing. Overexpressing two members of the complex, Mulder and Roswell, is also lethal, and in the case of Mulder, causes abnormal mitochondrial morphology. These data are the first evidence that defective mt:RNase P causes mitochondrial dysfunction, lethality and aberrant mitochondrial tRNA processing in vivo, underscoring its physiological importance. This in vivo mt:RNase P model will advance our understanding of how loss of mitochondrial tRNA processing causes tissue failure, an important aspect of human mitochondrial disease.
Insights
Mitochondrial RNase P (mt:RNase P) complex proteins are essential for mitochondrial function and viability. Defective mt:RNase P in Drosophila causes mitochondrial deficits and lethality due to impaired tRNA processing.
Area of Science:
- Mitochondrial biology
- Molecular genetics
- Biochemistry
Background:
- Mitochondrial DNA encodes essential proteins translated using mitochondrially encoded tRNAs and rRNAs.
- Mitochondrial tRNAs require processing for functionality, similar to nuclear tRNAs.
- The mitochondrial ribonuclease P (mt:RNase P) complex, comprising MRPP1, MRPP2, and PRORP, is crucial for 5'-end tRNA maturation.
Purpose of the Study:
- To identify and characterize the components of Drosophila mt:RNase P.
- To investigate the in vivo function and developmental impact of mt:RNase P.
- To elucidate the consequences of impaired mt:RNase P activity on mitochondrial health and tRNA processing.
Main Methods:
- Homology searches to identify Drosophila mt:RNase P protein homologs (Mulder, Scully, Roswell).
- Gene knockdown and overexpression studies in Drosophila.
- Mitochondrial localization assays.
- Assessment of mitochondrial function and tRNA processing efficiency.
Main Results:
- Drosophila mt:RNase P consists of Mulder (PRORP), Scully (MRPP2), and Roswell (MRPP1).
- Each component is essential, localizes to mitochondria, and is required for viability.
- Reduced levels of these proteins lead to mitochondrial deficits and defective mitochondrial tRNA processing.
- Overexpression of Mulder or Roswell causes lethality, with Mulder overexpression inducing abnormal mitochondrial morphology.
Conclusions:
- This study provides the first in vivo evidence linking defective mt:RNase P to mitochondrial dysfunction, lethality, and aberrant mitochondrial tRNA processing.
- The identified Drosophila mt:RNase P complex is physiologically important for maintaining mitochondrial health.
- This model system will advance understanding of how mitochondrial tRNA processing defects contribute to tissue failure and human mitochondrial diseases.
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