The Leptomonas collosoma spliced leader RNA can switch between two alternate structural forms

Area of Science:

• Molecular Biology
• RNA Structure
• Parasitology

Background:

• Spliced leader RNA (SL RNA) plays a crucial role in gene expression in trypanosomatids.
• Previous models proposed a general structure for the 3' half of SL RNA.

Purpose of the Study:

• To investigate the secondary structure of Leptomonas collosoma spliced leader RNA.
• To elucidate the structural dynamics of the 5' half of SL RNA, including the splice site.

Main Methods:

• Combination of physical and molecular biological techniques.
• Analysis of RNA secondary structures and their stability.
• Investigation of structural interconversion dynamics.

Main Results:

• Confirmed the proposed structure for the 3' half of SL RNA, featuring stem loops and a single-stranded region.
• Identified two competing secondary structures in the 5' half of SL RNA with similar stability.
• Observed fast interconversion (<1 s) between these 5' half structures.
• The favored conformation includes a stable hairpin helix involving the splice site and the 5' end of SL RNA.
• This helix exhibits unusual nuclease sensitivity and thermal stability, suggesting tertiary interactions.

Conclusions:

• The 5' half of Leptomonas collosoma SL RNA exists in dynamic structural conformations.
• The favored structure may be stabilized by tertiary interactions.
• These findings offer insights into RNA-RNA interactions and splicing mechanisms, with parallels to mammalian splicing.