Loss of Individual Mitochondrial Ribonuclease P Complex Proteins Differentially Affects Mitochondrial tRNA Processing In Vivo.

Maithili Saoji,Rachel T Cox,Aditya Sen

doi:10.3390/ijms22116066

Abstract

Over a thousand nucleus-encoded mitochondrial proteins are imported from the cytoplasm; however, mitochondrial (mt) DNA encodes for a small number of critical proteins and the entire suite of mt:tRNAs responsible for translating these proteins. Mitochondrial RNase P (mtRNase P) is a three-protein complex responsible for cleaving and processing the 5′-end of mt:tRNAs. Mutations in any of the three proteins can cause mitochondrial disease, as well as mutations in mitochondrial DNA. Great strides have been made in understanding the enzymology of mtRNase P; however, how the loss of each protein causes mitochondrial dysfunction and abnormal mt:tRNA processing in vivo has not been examined in detail. Here, we used Drosophila genetics to selectively remove each member of the complex in order to assess their specific contributions to mt:tRNA cleavage. Using this powerful model, we find differential effects on cleavage depending on which complex member is lost and which mt:tRNA is being processed. These data revealed in vivo subtleties of mtRNase P function that could improve understanding of human diseases.

Highlights

The mitochondrial genome in metazoans is highly conserved, encoding the same 13 oxidative phosphorylation proteins, 2 ribosomal RNAs, and a complete set of 22 transfer RNAs required for translation [1]
In mitochondria, human mtRNase P carries out this function. mtRNase P is a three-protein complex comprised of mitochondrial ribonuclease P proteins (MRPP) 1, 2, and 3 (Figure 1A) [4]
The scu alleles are ethyl methanesulfonate (EMS) induced mutations, and the rswl mutant phenotype was produced by a single available RNA interference (RNAi) knockdown strain

Summary

Introduction

The mitochondrial genome in metazoans is highly conserved, encoding the same 13 oxidative phosphorylation proteins, 2 ribosomal RNAs (mt:rRNA), and a complete set of 22 transfer RNAs (mt:tRNAs) required for translation [1]. In the metazoan mitochondrial genome, mRNAs and rRNAs are interspersed by tRNAs, an organization that is commonly referred to as the tRNA punctuation model [3]. With this arrangement, correctly processed mt:tRNAs release the other mtRNA products through the action of mitochondrial (mt) RNase P and RNase Z (ELAC2) acting at mt:tRNA 50 - and 30 -ends, respectively [4,5]. MRPP3, a homolog of the single subunit PRORPs present in the nucleus and organelles of land plants, is the catalytic metallo-endonuclease that cleaves mt:tRNAs at the 50 -end [4,12,13,14].

Methods

Results

Conclusion