Structure of a group II intron in complex with its reverse transcriptase.

Area of Science:

• Molecular Biology
• RNA catalysis
• Genetics

Background:

• Bacterial group II introns are catalytic RNAs with retroelement properties.
• They self-splice and integrate into DNA targets via reverse transcription.
• Group II introns form ribonucleoprotein complexes with intron-encoded proteins.

Purpose of the Study:

• To determine the cryo-electron microscopy (cryo-EM) structures of a group IIA intron.
• To elucidate the functional coordination between intron RNA and its encoded protein.
• To investigate evolutionary relationships between group II introns and other genetic elements.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to resolve structures.
• Structures were determined for both the ribonucleoprotein complex and protein-depleted forms.
• High-resolution imaging (3.8-Å and 4.5-Å) was achieved.

Main Results:

• The structure of the Lactococcus lactis group IIA intron ribonucleoprotein complex was determined at 3.8-Å resolution.
• The protein-depleted intron structure was resolved at 4.5-Å resolution.
• The intron-encoded protein's reverse transcriptase domain shows similarity to telomerase, and the splicing center resembles spliceosomal Prp8.

Conclusions:

• The structures reveal functional coordination between group II intron RNA and protein.
• Intriguing structural similarities suggest deep evolutionary connections between group II introns, telomerase, and spliceosomes.
• These findings offer new insights into RNA splicing and retroelement mobility.