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Disruption of a gene encoding a novel mitochondrial DEAD-box protein in Trypanosoma brucei affects edited mRNAs
A Missel1, A E Souza, G Nörskau
1Laboratorium für molekulare Biologie, Genzentrum der Ludwig-Maximilians-Universität München, Martinsried, Germany.
Abstract:
The majority of mitochondrial pre-mRNAs in kinetoplastid protozoa such as Trypanosoma, Leishmania, and Crithidia are substrates of a posttranscriptional processing reaction referred to as RNA editing. The process results in the insertion and, to a lesser extent, deletion of uridylates, thereby completing the informational content of the mRNAs. The specificity of the RNA editing reaction is provided by guide RNAs (gRNAs), which serve as templates for the editing apparatus. In addition, the process relies on mitochondrial proteins, presumably acting within a high-molecular-mass ribonucleoprotein complex. Although several enzymatic activities have been implicated in the editing process, no protein has been identified to date. Here we report the identification of a novel mitochondrial DEAD-box protein, which we termed mHel61p. Disruption of the mHEL61 alleles in insect-stage Trypanosoma brucei cells resulted in a reduced growth rate phenotype. On a molecular level, the null mutant showed significantly reduced amounts of edited mRNAs, whereas never-edited and nuclear mRNAs were unaffected. Reexpression of mHel61p in the knockout cell line restored the ability to efficiently synthesize edited mRNAs. The results suggest an involvement of mHel61p in the control of the abundance of edited mRNAs and thus reveal a novel function for DEAD-box proteins.
Insights
Researchers identified a novel mitochondrial protein, mHel61p, crucial for RNA editing in Trypanosoma brucei. This DEAD-box protein controls the abundance of edited messenger RNAs (mRNAs), revealing a new function for this protein family.
Area of Science:
- Molecular Biology
- Genetics
- Parasitology
Background:
- Kinetoplastid protozoa extensively use RNA editing to process mitochondrial pre-mRNAs.
- Guide RNAs (gRNAs) direct RNA editing, which involves uridylate insertion/deletion.
- The editing machinery involves mitochondrial proteins within a ribonucleoprotein complex, but key components remained unidentified.
Purpose of the Study:
- To identify novel proteins involved in mitochondrial RNA editing in kinetoplastids.
- To elucidate the function of identified proteins in the RNA editing process.
- To investigate the role of DEAD-box proteins in Trypanosoma brucei RNA editing.
Main Methods:
- Genetic disruption of the mHEL61 gene in Trypanosoma brucei.
- Analysis of growth rates in wild-type versus knockout cell lines.
- Quantification of edited and unedited mRNA levels using molecular techniques.
- Complementation of the knockout phenotype by reexpressing mHel61p.
Main Results:
- Identification of a novel mitochondrial DEAD-box protein, mHel61p.
- Disruption of mHEL61 led to reduced cell growth and significantly decreased levels of edited mRNAs.
- Nuclear and never-edited mRNAs were unaffected by the mHEL61 disruption.
- Reintroduction of mHel61p restored efficient edited mRNA synthesis.
Conclusions:
- mHel61p is essential for efficient mitochondrial RNA editing in Trypanosoma brucei.
- This study reveals a novel function for DEAD-box proteins in regulating the abundance of edited mRNAs.
- mHel61p plays a critical role in posttranscriptional RNA processing in kinetoplastid mitochondria.