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Related Concept Videos

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Ribosome synthesis is a highly complex and coordinated process involving more than 200 assembly factors. The synthesis and processing of ribosomal components occurs not only in the nucleolus but also in the nucleoplasm and the cytoplasm of eukaryotic cells.
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Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
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Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death.  Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
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The inner mitochondrial membrane is the primary site of ATP synthesis. The inner membrane domain that forms a smooth layer adjacent to the outer membrane is called the inner boundary membrane. This domain contains membrane transporters that drive metabolites in and out of the mitochondria.  In contrast, the inner membrane network that invaginates into the matrix space is called the cristae membrane. This domain accounts for principle mitochondrial function as it accommodates the protein...
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The mitochondrial methylation potential gates mitoribosome assembly.

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Mitochondrial S-adenosylmethionine (SAM) is crucial for processing mitochondrial ribosomal RNA and assembling mitoribosomes. Its absence stalls ribosome biogenesis, impacting mitochondrial gene expression and translation.

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Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • S-adenosylmethionine (SAM) is the primary methyl donor in cells.
  • SAM is vital for mitochondrial gene expression, including RNA modifications, translation, and ribosome biogenesis.

Purpose of the Study:

  • To investigate the role of mitochondrial SAM in mitochondrial ribosomal gene processing and mitoribosome assembly.
  • To elucidate the structural and functional impact of SAM deficiency on mitochondrial translation.

Main Methods:

  • Direct long-read RNA sequencing in mouse tissues and embryonic fibroblasts.
  • Proteomic analysis of ribosome fractions.
  • Cryo-electron microscopy for structural analysis.

Main Results:

  • Mitochondrial SAM deficiency leads to failure in processing the mitochondrial ribosomal gene cluster, accumulating unprocessed precursors.
  • Precursors were found associated with processing and assembly factors, indicating stalled mitoribosome biogenesis.
  • SAM-dependent methylation is essential for peptidyl transferase center formation during mitoribosome assembly.

Conclusions:

  • SAM plays a critical role in coordinating mitochondrial ribosomal RNA processing and large subunit maturation.
  • Cellular methylation capacity is directly linked to mitochondrial translation capacity through SAM-dependent processes.