We have revealed structures of human pseudouridine synthase 3 in a complex with tRNA
Figure caption
Lin and Kleemann et al. explore the molecular mechanisms that drive the specificity of human PUS3 and show that the formation of its homodimer is ultimately necessary for the specific modification of tRNAs.
(Artwork by Ting-Yu Lin)
During my previous work at Malopolska Centrum Biotechnology in Jagiellonian University (Poland), I worked with Dr. Sebastian Glatt (https://glatt-lab.pl/) and determined the first cryo-electron microscopy (cryo-EM) structures of the long-neglected human enzyme PUS3 (https://doi.org/10.1016/j.molcel.2024.06.013).
Here is the quote from original press release.
“The current study reveals not just the structure of the resting human PUS3, which is ‘waiting’ for its target substrate, but also in complex with different tRNA molecules. This gallery of structures shows that two identical PUS3 enzyme molecules form a so-called homodimer, which is crucial for both the structural integrity of the protein and its capability to bind tRNAs. Only in this homodimer configuration, the correct uridine is positioned near the active site of one PUS3 monomer, while another region of the tRNA contacts the second monomer. Therefore, the cryo-EM structures illustrate how PUS3 accurately places the target uridine in the catalytic site for the subsequent modification reactions – explaining its specificity and mechanism at the atomic level.
To better understand the prevalence of pseudouridylation sites in the cell, the Leidel group in Switzerland (https://leidel.dcbp.unibe.ch/) used engineered human cell lines and they confirmed that PUS1 and PUS3 target different sets of cellular RNAs. While PUS1 targets a wide range of RNAs, including tRNAs and messenger RNAs (mRNAs), the PUS3 specifically modifies only tRNAs. Last but not least, the authors established a reporting system to express clinically relevant PUS3 variants using human cell lines, enabling them to monitor and confirm the impacts of different clinical mutations on the activity of the enzyme. These cell culture experiments were carried out in collaboration with the neighbouring Faculty of Biochemistry, Biophysics, and Biotechnology (WBBB) at the JU (https://wbbib.uj.edu.pl/en_GB/wydzial/zaklady-i-pracownie/zaklad-biochemii-komorki).”
Figure caption
Lin and Kleemann et al. explore the molecular mechanisms that drive the specificity of human PUS3 and show that the formation of its homodimer is ultimately necessary for the specific modification of tRNAs.
(Artwork by Dominika Dobosz)
