12. Jan. 2024

The fact that scientists must not be satisfied with common assumptions has been confirmed once again by researchers from CEITEC Masaryk University, who are investigating telomerase ribonucleic acid (TR), which plays an important role in DNA resynthesis at the ends of chromosomes. For this function, it is crucial that the part of TR that is used to replenish the ends of chromosomes, is single-stranded and thus open. The closed structure is in turn important for other TR functions. Previous studies have often relied on computer predictions combined with experimental data and tentative assumptions to determine TR structure. However, CEITEC scientists have taken the route of analysing individual TR molecules and have shown that in cells, TR is not always assembled into a single uniform shape, but occurs there in several different states existing side by side. This finding will allow better elucidation of the wide range of biological processes in cells in which these RNAs are involved.

Telomeres, the protective structures at the ends of chromosomes, are maintained by telomerase, a specific enzyme complex composed of RNA and proteins. Cells that do not have active telomerase stop dividing and/or die. The crucial component of telomerase is telomerase RNA, which scientists at CEITEC Masaryk University have now shown to be structurally dynamic, i.e. that its structure can change during the biological processes in which it is involved: when the telomerase complex is assembled from its individual components, telomerase RNA appears in a closed structure, but when it is doing its job of renewing telomeres, its open structure is necessary. These results are also consistent with findings that have been obtained before using a much more sophisticated NMR method in other organisms.

The main author of the research, Lucie Bozděchová, led by molecular biologist Jiří Fajkus, focused on the discrepancies between the presentations of the results of earlier works, which showed an open structure in different TRs, although the experimental data itself showed a closed structure, which would not be functional during telomerase action. Therefore, it was common to combine the experimental results with the initial assumption that the TR structure was open and "adjust" the results accordingly. Instead, the CEITEC researchers used a novel approach to analyse the experimental data by first evaluating all the structures of individual RNA molecules co-existing in the sample without any prior assumptions, and then grouping these structures according to their similarity to each other. "With this new approach, we were able to show that one of the obtained telomerase RNA structure types (corresponding to about one-third of the cases of structures found) corresponded to open structure, while the majority of the structures evaluated corresponded to closed structures. The classical method of evaluation showed only closed structures on the same data," comments Lucie Bozděchová, who carried out the research with the support of Career Restart (GAMU) and EXPRO (GAČR) grants.

Crucial to this scientific finding was the bioinformatic analysis carried out by Kateřina Havlová from the Faculty of Science of Masaryk University, based on a method recently developed by Dr. Yiliang Ding from the John Innes Centre, UK. Thanks to this, scientists have gained a more realistic picture of the different structures of telomerase RNA and possible transitions between them, moreover, in an important model organism - the moss Physcomitrium patens, for which experimental structural data were completely lacking until now.

An approach that relies on the analysis of the structure of individual RNA molecules, rather than on the detection of only one majority structure from averaged results, can now be used much more widely in the analysis of all RNAs whose function depends on their spatial structure and the dynamic transitions between different RNA structural states.

The research has been published in the Journal of Molecular Biology.

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