Hierarchical RNA Processing Is Required for Mitochondrial Ribosome Assembly.

Area of Science:

• Mitochondrial biology
• Molecular genetics
• Biochemistry

Background:

• The precise regulation of mitochondrial RNA processing and its impact on ribosome biogenesis and energy metabolism remain incompletely understood.
• Mitochondrial dysfunction is implicated in various diseases, underscoring the need to elucidate fundamental cellular processes.

Purpose of the Study:

• To investigate the role of the endoribonuclease component of RNase P complex, MRPP3, in mitochondrial RNA processing.
• To determine the consequences of MRPP3 deficiency on mitochondrial function, ribosome biogenesis, and organismal health.

Main Methods:

• Generation and analysis of conditional knockout mice for MRPP3.
• Transcriptome-wide parallel analyses of RNA ends (PARE) and RNA sequencing (RNA-seq).
• Investigation of mitoribosomal protein complex assembly.

Main Results:

• MRPP3 is essential for life; its specific knockout in heart and skeletal muscle causes severe cardiomyopathy.
• In vivo 5' tRNA cleavage precedes 3' tRNA processing, a crucial step for mitochondrial ribosomal subunit biogenesis.
• Mitoribosomal biogenesis occurs co-transcriptionally, with large mitoribosomal proteins forming a subcomplex on unprocessed 16S rRNA.

Conclusions:

• MRPP3 activity is non-redundant and critical for preventing cardiomyopathy.
• Mitochondrial RNA processing, specifically tRNA cleavage, is a prerequisite for proper mitoribosome assembly.
• RNA processing acts as a crucial link between transcription and translation in the assembly of the mitoribosome.