Related Experiment Video
Updated: Aug 18, 2026
Analysis of the Expression and Complexes Assembly of the Mitochondrial Respiratory Chain Proteins in the Fission Yeast Schizosaccharomyces pombe
Published on: May 2, 2025
Transcription and RNA-processing in fission yeast mitochondria
Bernd Schäfer1, Monika Hansen, B Franz Lang
1Department of Biology IV (Microbiology), RWTH Aachen University, Worringer Weg, 52056 Aachen, Germany. bernd.schaefer@rwth-aachen.de
Abstract:
We systematically examined transcription and RNA-processing in mitochondria of the petite-negative fission yeast Schizosaccharomyces pombe. Two presumptive transcription initiation sites at opposite positions on the circular-mapping mtDNA were confirmed by in vitro capping of primary transcripts with guanylyl-transferase. The major promoter (Pma) is located adjacent to the 5'-end of the rnl gene, and a second, minor promoter (Pmi) upstream from cox3. The primary 5'-termini of the mature rnl and cox3 transcripts remain unmodified. A third predicted accessory transcription initiation site is within the group IIA1 intron of the cob gene (cobI1). The consensus promoter motif of S. pombe closely resembles the nonanucleotide promoter motifs of various yeast mtDNAs. We further characterized all mRNAs and the two ribosomal RNAs by Northern hybridization, and precisely mapped their 5'- and 3'-ends. The mRNAs have leader sequences with a length of 38 up to 220 nt and, in most instances, are created by removal of tRNAs from large precursor RNAs. Like cox2 and rnl, cox1 and cox3 are not separated by tRNA genes; instead, transcription initiation from the promoters upstream from rnl and cox3 compensates for the lack of tRNA-mediated 5'-processing. The 3'-termini of mRNAs and of SSU rRNA are processed at distinct, C-rich motifs that are located at a variable distance (1-15 nt) downstream from mRNA and SSU-rRNA coding regions. The accuracy of RNA-processing at these sites is sequence-dependent. Similar 3'-RNA-processing motifs are present in species of the genus Schizosaccharomyces, but not in budding yeasts that have functionally analogous A+T-rich dodecamer processing signals.
Insights
This study reveals transcription initiation sites and RNA processing mechanisms in Schizosaccharomyces pombe mitochondria. Distinct C-rich motifs guide accurate 3' RNA processing, differing from budding yeasts.
Area of Science:
- Mitochondrial Gene Expression
- RNA Biology
- Yeast Genetics
Background:
- Mitochondrial transcription and RNA processing are crucial for cellular respiration.
- Schizosaccharomyces pombe, a petite-negative yeast, offers a unique model for studying these processes.
- Understanding these mechanisms is key to deciphering mitochondrial function and evolution.
Purpose of the Study:
- To systematically examine transcription initiation and RNA processing in Schizosaccharomyces pombe mitochondria.
- To identify and characterize promoter elements and RNA processing signals.
- To compare these mechanisms with those in other yeast species.
Main Methods:
- In vitro capping with guanylyl-transferase to confirm transcription initiation sites.
- Northern hybridization to characterize mature transcripts (mRNAs and ribosomal RNAs).
- Precise mapping of 5' and 3' ends of RNA molecules.
Main Results:
- Identified two major transcription initiation sites (Pma and Pmi) and a third accessory site.
- Confirmed promoter motifs in S. pombe resemble those in other yeast mitochondrial DNAs.
- Demonstrated that mRNAs are often generated by tRNA removal from precursor RNAs, with exceptions compensated by specific transcription initiation.
- Mapped distinct, C-rich 3'-RNA processing motifs, crucial for accurate processing of mRNAs and SSU rRNA.
- Showcased sequence-dependent accuracy of RNA processing at these motifs.
Conclusions:
- Schizosaccharomyces pombe utilizes specific transcription initiation and C-rich motifs for mitochondrial RNA processing.
- These mechanisms differ from the A+T-rich dodecamer signals found in budding yeasts.
- The findings provide insights into the diversity of mitochondrial gene expression regulation in yeasts.
Related Concept Videos
02:53Ribosomal RNA Synthesis
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...
02:53Ribosomal RNA Synthesis
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...
01:35Pre-mRNA Processing: Modification of pre-mRNA Ends
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a cap to the 5' end of the growing transcript. In this process, a 5' phosphate is replaced by modified guanosine that has a methyl group attached (7-methyl guanosine). This 5' cap helps the cell...
01:10Transcription
Transcription is the process of synthesizing RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene sequence. Additionally, many other proteins and regulatory sequences are involved in the proper synthesis of messenger RNA (mRNA). Regulation of transcription is responsible for the differentiation of all the different types of cells and often for the proper cellular response to environmental signals.
Transcription Can Produce Different Kinds...
01:17Transcription
Transcription Can Produce Different Kinds of RNA Molecules
In eukaryotes,...
01:19Translocation of Proteins into the Mitochondria
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...