Defining the chemical groups essential for Tetrahymena group I intron function by nucleotide analog interference...

Area of Science:

• Biochemistry
• Molecular Biology
• RNA Structure and Function

Background:

• Identifying essential chemical groups in RNA requires high-resolution biochemical methods.
• The Tetrahymena group I intron's catalytic activity depends on specific RNA chemical functionalities.
• Previous studies indicated guanosine residues are crucial but lacked a comprehensive mapping approach.

Purpose of the Study:

• To develop and apply a novel nucleotide analog interference mapping (NAIM) assay.
• To simultaneously and individually assess the contribution of N2 exocyclic amines of guanosine within large RNA molecules.
• To identify specific guanosine residues critical for the ligation activity of the Tetrahymena group I intron.

Main Methods:

• Utilized 5'-O-(1-thio)inosine monophosphate (IMPαS) in a NAIM assay.
• Applied IMPαS to probe the role of N2 exocyclic amines of guanosine in RNA ligation.
• Employed 5'-O-(1-thio)diaminopurine riboside monophosphate (DMPαS) for interference rescue experiments.

Main Results:

• Identified three phylogenetically conserved guanosines (G111, G112, G303) essential for 3' exon ligation.
• Determined that guanosine G22 and others in the P1 helix are vital for 5' exon ligation.
• Demonstrated rescue of G22A and G303A point mutations using DMPαS, confirming the role of the N2 amino group.

Conclusions:

• The NAIM assay effectively maps essential guanosine N2 exocyclic amines in large RNAs.
• Specific guanosines are critical for distinct catalytic steps (5' and 3' exon ligation) of the Tetrahymena group I intron.
• This method provides a powerful tool for analyzing RNA and DNA chemical group functionalities and can be extended with other analogs.