Reverse transcriptase activity associated with maturase-encoding group II introns in yeast mitochondria

Area of Science:

• Molecular Biology
• Genetics
• Yeast Mitochondria

Background:

• Group II introns are mobile genetic elements found in various organisms.
• Mitochondrial DNA (mtDNA) in yeast harbors specific introns, including al1 and al2 in the COX1 gene.
• These introns encode proteins with reverse transcriptase-like activity, crucial for RNA splicing.

Purpose of the Study:

• To investigate the reverse transcriptase activity associated with yeast mitochondrial Group II introns al1 and al2.
• To determine the template specificity and initiation sites of this reverse transcriptase.
• To elucidate the role of these introns and their encoded enzymes in RNA splicing and potential retroelement activity.

Main Methods:

• Analysis of ribonucleoprotein particles from yeast mitochondria.
• Characterization of reverse transcriptase activity using specific intron RNA and pre-mRNA templates.
• Utilizing a mutant yeast strain with enhanced reverse transcriptase activity.

Main Results:

• Yeast mitochondria contain a reverse transcriptase activity linked to introns al1 and al2.
• This activity exhibits high specificity for the introns and flanking exons of the COX1 gene.
• The reverse transcriptase uses either excised intron RNA or COX1 pre-mRNA as a template, initiating cDNA synthesis at specific sites.

Conclusions:

• Group II introns al1 and al2 function as retroelements within yeast mitochondria.
• The encoded reverse transcriptases are adapted for RNA splicing, demonstrating a dual role in genetic processes.
• These findings provide insights into intron-exon interactions and mobile genetic element evolution in mitochondria.