A novel cloverleaf structure found in mammalian mitochondrial tRNA(Ser) (UCN)

Area of Science:

• Molecular Biology
• RNA Structure
• Mitochondrial Genetics

Background:

• Bovine mitochondrial tRNA(Ser) (UCN) gene sequence suggested two U-U mismatches in the acceptor stem.
• This predicted unusual structure lacked experimental confirmation at the RNA level.

Purpose of the Study:

• To isolate and determine the complete sequence and structure of bovine liver mitochondrial tRNA(Ser) (UCN).
• To investigate the structural characteristics and potential evolutionary conservation of this mitochondrial tRNA.

Main Methods:

• Isolation of bovine liver mitochondrial tRNA(Ser) (UCN).
• Determination of the complete RNA sequence, including modified nucleotides.
• Enzymatic probing to elucidate the secondary structure (cloverleaf).

Main Results:

• The tRNA(Ser) (UCN) initiated from the third nucleotide of the putative gene, not the first.
• An unusual cloverleaf structure was identified with a single nucleotide between the acceptor and D stems, and a 6 base-pair anticodon stem.
• This specific cloverleaf structure is conserved in mammalian mitochondrial tRNA(Ser) (UCN) genes (human, rat, mouse) but absent in non-mammals (chicken, frog).

Conclusions:

• Bovine mitochondrial tRNA(Ser) (UCN) possesses a unique secondary structure confirmed at the RNA level.
• This unusual structure, characterized by specific stem lengths and loop sizes, is a conserved feature in mammalian mitochondrial tRNA(Ser) (UCN).
• The findings highlight evolutionary adaptations in mitochondrial tRNA structure within mammals.