How archaeal ribosomes hibernate
Translation of the article by Sylvain Guilbaud, Scientific communication, Ecole Polytechnique
The scientists used microscopes at the Cimex facility at the École Polytechnique to image the ribosomes and reconstruct them in 3D.
The Laboratory of Structural Cell Biology (BIOC*), in collaboration with Ifremer in Brest, the CBI in Toulouse, and the Pasteur Institute, has identified a molecule in archaea capable of putting a cellular machinery essential to cells—the ribosome—on hold. This “hibernation factor” binds to the ribosome when external conditions are unfavorable.
Ribosomes play a key role: they assemble proteins from genetic information in all living organisms. These proteins then carry out all the functions necessary for life. A ribosome consists of two subunits: a small one responsible for reading the messenger RNA that contains the genetic information, and a large one that assembles the corresponding protein. Present by the thousands in every cell, these ribosomes are massive and consume a great deal of energy.
However, when energy becomes scarce, a way must be found to shut down the ribosomes and protect them from degradation until conditions become favorable again. In a paper published in *Nature Communications*, the “Translation Mechanisms” team at BIOC reveals a protein capable of putting archaeal ribosomes into “hibernation.”
Archaea are single-celled organisms that differ from bacteria (which are also single-celled and lack a nucleus) and are closely related to eukaryotes (a group that includes all living organisms whose cells have a nucleus). Recent studies show that they are found in all types of environments, even in the human microbiome! Like all living organisms, archaea are subject to environmental fluctuations and must adapt their energy consumption accordingly.
“Ribosomal hibernation factors were already well known in bacteria and eukaryotes. But before we began our work, none had been identified in archaea,” explains Clément Madru, assistant professor in the Department of Biology at École Polytechnique and co-first author of the article alongside Gabrielle Bourgeois (BIOC) and Rémi Dulermo (Ifremer).
Scientists subjected Pyrococcus abyssi archaea to temperature and oxygen stress. This hyperthermophilic archaeon normally grows in the absence of oxygen, in the abyssal trenches of the Pacific Ocean. They then purified the ribosomes from these stressed cells. Finally, using the cryo-electron microscope at the École Polytechnique’s Interdisciplinary Microscopy Center (CIMEX), a very large number of ribosomes were examined in minute detail, making it possible to reconstruct their three-dimensional structure—one of BIOC’s areas of expertise.
Most of the ribosomes in the sample were bound to a molecule whose function was previously unknown, named HibA. One part of HibA, similar to a molecule already known in other organisms, can bind to the small subunit of the ribosome in place of messenger RNA. The other part binds to functional sites on the large subunit.
Caption: Ribosomal structures from the archaeon *Pyrococcus abyssi*. On the left, an active ribosome associated with transfer RNAs (tRNAs) involved in protein synthesis. On the right, the hibernation factor HibA bound to ribosomes observed in various states. HibA binds to the interface between the large subunit (50S) and the small subunit (30S).
These bonds prevent the ribosome from functioning, causing it to “hibernate.” “It’s also a way to hold the two subunits together to prevent the ribosome from dissociating. This helps protect it from degradation while it waits for better conditions,” notes Clément Madru. “Furthermore, HibA can occupy different positions within the ribosome. This is the first time a hibernation factor has been identified with multiple binding sites.”
The data also show that HibA can bind to molecules that supply energy to the cell. “This may be related to its ability to block ribosomes, but it’s still just a hypothesis we’re working on,” says the researcher. Beyond unraveling cellular mechanisms, the comparative study of ribosomes found in different types of organisms sheds light on the overall evolution of life.
Reference :
Madru, C., Bourgeois, G., Dulermo, R. et al. A family of ribosome hibernation factors widespread in Archaea. Nat Commun (2026). https://doi.org/10.1038/s41467-026-72341-8
*BIOC : joint reseauc unit; CNRS, École polytechnique, Institut Polytechnique of Paris, 91120 Palaiseau, France
**The collaboration includes scientists from BIOC, Ifremer, the University of Toulouse, Paris-Cité University, and the Pasteur Institute.