Related Experiment Video
Updated: Sep 9, 2025
07:31
ACT1-CUP1 Assays Determine the Substrate-Specific Sensitivities of Spliceosomal Mutants in Budding Yeast
Published on: June 30, 2022
2.6K
Cysteine Mutagenesis of a Group II Intron-Encoded Protein Supports Splicing, Mobility, and Site-Specific Labeling
Jasmine A Harper1, Sarah A Starcovic1, Neil Billington1
1Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia 26506, United States.
Biochemistry
|August 29, 2025
Summary
Group II introns use intron-encoded proteins (IEPs) for splicing and DNA integration. Mutating conserved cysteines in the IEP did not affect splicing but altered reverse transcription, enabling fluorescent labeling for real-time RNP studies.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Group II introns are mobile genetic elements that splice from RNA and integrate into DNA via retrohoming.
- Intron-encoded proteins (IEPs) are essential reverse transcriptases that facilitate splicing and RNP complex formation.
Purpose of the Study:
- Investigate the role of conserved cysteine residues in the IEP of the group IIC intron *Ta.it.I1* from *Thermoanaerobacter italicus*.
- Assess the impact of cysteine mutations on IEP splicing, reverse transcription (RT) activity, and retromobility.
- Develop a method for site-specific fluorescent labeling of the IEP to visualize RNP dynamics.
Main Methods:
- Site-directed mutagenesis of conserved cysteine residues in the IEP to methionine.
- Assays for RNA splicing efficiency and reverse transcription activity.
- Maleimide-thiol chemistry for site-specific fluorescent labeling of the IEP.
- Monitoring RNA binding and RNP assembly using labeled IEPs.
Main Results:
- Cysteine substitutions generally retained wild-type splicing efficiency and retromobility.
- Mutations in the thumb domain enhanced RT activity, while those near the YADD motif reduced it.
- Complete cysteine removal allowed successful site-specific fluorescent labeling without compromising IEP function.
- Labeled IEPs enabled real-time visualization of RNA binding and RNP complex assembly.
Conclusions:
- Conserved cysteines in the *Ta.it.I1* IEP are not essential for splicing or retromobility but influence RT activity.
- Site-specific fluorescent labeling of the IEP is feasible and provides a powerful tool for studying RNP dynamics.
- IEP-intron interactions exhibit structural flexibility, allowing for functional labeling and real-time analysis.
