A cis-acting A-U sequence element induces kinetoplastid U-insertions

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• RNA editing is a crucial post-transcriptional modification process in kinetoplastids.
• Guide RNA (gRNA)-directed editing is well-established, but guide RNA-independent mechanisms are less understood.
• The cytochrome b mRNA in Leishmania tarentolae undergoes U-insertion editing.

Purpose of the Study:

• To investigate the role of a specific upstream A-U sequence in guide RNA-independent U-insertion.
• To determine if this sequence can induce editing in heterologous transcripts.
• To explore the mechanism underlying this novel editing process.

Main Methods:

• In vitro assays using mitochondrial extracts from Leishmania tarentolae.
• Analysis of U-nucleotide insertion sites relative to the A-U sequence.
• Transfection of mammalian cells with transcripts containing the A-U sequence.

Main Results:

• A 34-nucleotide A-U sequence upstream of editing sites induced U-insertions without guide RNA.
• U-insertions occurred at specific positions flanking the A-U sequence.
• The A-U sequence alone was sufficient to induce editing in a mammalian transcript.
• The A-U sequence shares similarity with known gRNA templating regions and other editing sites.
• A protein was identified that specifically interacts with the A-U sequence.

Conclusions:

• The A-U sequence acts as a cis-acting element, driving guide RNA-independent U-insertion editing.
• This mechanism may represent a conserved feature of RNA editing in kinetoplastids.
• The findings support a model where proteins interacting with specific RNA sequences can mediate editing.