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Updated: Jun 26, 2025
Polysome Profiling in Leishmania, Human Cells and Mouse Testis
Published on: April 8, 2018
Structural and mechanistic insights into the function of Leishmania ribosome lacking a single pseudouridine
K Shanmugha Rajan1, Saurav Aryal2, Disha-Gajanan Hiregange3
1Department of Chemical and Structural Biology, The Weizmann Institute of Science, Rehovot 76100001, Israel; The Mina and Everard Goodman Faculty of Life Sciences and Advanced and Nanotechnology Institute, Bar-Ilan University, Ramat-Gan 52900, Israel.
Abstract:
Leishmania is the causative agent of cutaneous and visceral diseases affecting millions of individuals worldwide. Pseudouridine (Ψ), the most abundant modification on rRNA, changes during the parasite life cycle. Alterations in the level of a specific Ψ in helix 69 (H69) affected ribosome function. To decipher the molecular mechanism of this phenotype, we determine the structure of ribosomes lacking the single Ψ and its parental strain at ∼2.4-3 Å resolution using cryo-EM. Our findings demonstrate the significance of a single Ψ on H69 to its structure and the importance for its interactions with helix 44 and specific tRNAs. Our study suggests that rRNA modification affects translation of mRNAs carrying codon bias due to selective accommodation of tRNAs by the ribosome. Based on the high-resolution structures, we propose a mechanism explaining how the ribosome selects specific tRNAs.
Insights
A single pseudouridine (Ψ) modification on ribosomal RNA (rRNA) is crucial for ribosome structure and function. This study reveals how this modification impacts tRNA selection during protein translation in Leishmania.
Area of Science:
- Molecular Biology
- Structural Biology
- Parasitology
Background:
- Leishmania parasites cause widespread cutaneous and visceral diseases.
- Pseudouridine (Ψ), a key rRNA modification, varies during the parasite life cycle.
- Altered pseudouridine levels in helix 69 (H69) impact ribosome function.
Purpose of the Study:
- To elucidate the molecular mechanism by which pseudouridine affects ribosome function.
- To determine the high-resolution structure of Leishmania ribosomes with and without a specific pseudouridine modification.
- To understand the role of pseudouridine in ribosome-tRNA interactions and translation.
Main Methods:
- Cryo-electron microscopy (cryo-EM) was used to determine ribosome structures.
- Structures were resolved at approximately 2.4-3 Å resolution.
- Comparative analysis of ribosomes with and without the H69 pseudouridine modification.
Main Results:
- The single pseudouridine modification in H69 significantly influences its structure.
- This modification is critical for interactions between H69, helix 44, and specific tRNAs.
- Ribosome structure, influenced by rRNA modification, affects the translation of codon-biased mRNAs.
Conclusions:
- Pseudouridine modification in rRNA is essential for maintaining ribosome structure and function.
- The study proposes a mechanism for how ribosomes select specific tRNAs based on structural insights.
- rRNA modification plays a key role in regulating translation, particularly for codon bias and tRNA accommodation.
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