Structural basis of RNA processing by human mitochondrial RNase P.

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Human mitochondrial transcripts are processed by mitochondrial RNase P (mtRNase P) and Z.
• Unlike bacterial or nuclear RNase P, mtRNase P is a protein complex, not a ribozyme.
• The exact mechanisms of RNA cleavage and methylation by mtRNase P have remained unclear.

Purpose of the Study:

• To elucidate the structural basis of human mtRNase P function.
• To reveal the mechanism of precursor tRNA recognition and processing by mtRNase P.
• To understand the roles of individual subunits in RNA cleavage and methylation.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine the structure of human mtRNase P bound to precursor tRNA.
• Biochemical assays to analyze substrate recognition and enzyme activity.

Main Results:

• The cryo-EM structure reveals a unique mechanism for substrate recognition and processing.
• The TRMT10C and SDR5C1 subunits form a subcomplex that binds conserved mitochondrial tRNA elements, including the anticodon loop.
• This subcomplex positions the tRNA for methylation and recruits the endonuclease PRORP for precise pre-tRNA cleavage.

Conclusions:

• The study provides the first structural insights into human mtRNase P.
• The findings reveal the molecular basis for the initial step of RNA processing in human mitochondria.
• This work clarifies the roles of TRMT10C, SDR5C1, and PRORP in mitochondrial tRNA maturation.