bims-mitran 2024-04-14 papers

Issue of 2024–04–14
three papers selected by
Andreas Kohler, Umeå University

Mitochondrion. 2024 Apr 09. pii: S1567-7249(24)00039-4. [Epub ahead of print]76 101881

The Schizosaccharomyces pombe DEAD-box protein Mss116 is required for mitoribosome assembly and mitochondrial translation.

Yirong Wang, Gang Feng, Ying Huang.

DEAD-box helicases are important players in mitochondrial gene expression, which is necessary for mitochondrial respiration. In this study, we characterized Schizosaccharomyces pombe Mss116 (spMss116), a member of the family of DEAD-box RNA helicases. Deletion of spmss116 in a mitochondrial intron-containing background significantly reduced the levels of mitochondrial DNA (mtDNA)-encoded cox1 and cob1 mRNAs and impaired mitochondrial translation, leading to a severe respiratory defect and a loss of cell viability during stationary phase. Deletion of mitochondrial introns restored the levels of cox1 and cob1 mRNAs to wide-type (WT) levels but could not restore mitochondrial translation and respiration in Δspmss116 cells. Furthermore, deletion of spmss116 in both mitochondrial intron-containing and intronless backgrounds impaired mitoribosome assembly and destabilization of mitoribosomal proteins. Our findings suggest that defective mitochondrial translation caused by deletion of spmss116 is most likely due to impaired mitoribosome assembly.

Keywords: DEAD-box protein; Mitochondrial translation; Mitoribosome assembly; OXPHOS, Respiration

DOI: https://doi.org/10.1016/j.mito.2024.101881

Annu Rev Biochem. 2024 Apr 09.

Replication and Transcription of Human Mitochondrial DNA.

Maria Falkenberg, Nils-Göran Larsson, Claes M Gustafsson.

Mammalian mitochondrial DNA (mtDNA) is replicated and transcribed by phage-like DNA and RNA polymerases, and our understanding of these processes has progressed substantially over the last several decades. Molecular mechanisms have been elucidated by biochemistry and structural biology and essential in vivo roles established by cell biology and mouse genetics. Single molecules of mtDNA are packaged by mitochondrial transcription factor A into mitochondrial nucleoids, and their level of compaction influences the initiation of both replication and transcription. Mutations affecting the molecular machineries replicating and transcribing mtDNA are important causes of human mitochondrial disease, reflecting the critical role of the genome in oxidative phosphorylation system biogenesis. Mechanisms controlling mtDNA replication and transcription still need to be clarified, and future research in this area is likely to open novel therapeutic possibilities for treating mitochondrial dysfunction.

DOI: https://doi.org/10.1146/annurev-biochem-052621-092014

Mitochondrion. 2024 Apr 08. pii: S1567-7249(24)00034-5. [Epub ahead of print] 101876

Role of Rmd9p in 3'-end processing of mitochondrial 15S rRNA in Saccharomyces cerevisiae.

Jitendra Singh, Sudhir Singh, Elhassan Ali Fathi Emam, Umesh Varshney.

Ribosome biogenesis, involving processing/assembly of rRNAs and r-proteins is a vital process. In Saccharomyces cerevisiae mitochondria, ribosomal small subunit comprises 15S rRNA (15S). While the 15S 5'-end processing uses Ccm1p and Pet127p, the mechanisms of the 3'-end processing remain unclear. We reveal involvement of Rmd9p in safeguarding/processing 15S 3'-end. Rmd9p deficiency results in a cleavage at a position 183 nucleotides upstream of 15S 3'-end, and in the loss of the 3'-minor domain. Rmd9p binds the 3'-end spacer sequence in 15S precursor, and a genetic interaction between rmd9 and dss1 indicates that Rmd9p regulates/limits mtEXO activity during the 3'-end spacer processing.

Keywords: Dss1p; Mitochondrial translation; RNA processing; Ribosome; Rmd9p

DOI: https://doi.org/10.1016/j.mito.2024.101876