RNAs (RiboNucleic Acids) are central to gene expression.
In the cells, RNAs all work in close association with proteins within so-called RNPs (RiboNucleoProtein particles). It doesn’t matter how big or small an RNA is, or in which steps of gene expression it is involved; RNAs are always intimately connected to proteins.
In the Lab, we are trying to understand how RNPs are put together and function.
Most of our work so far has focused on a very large RNP called the Ribosome.
The Ribosome is made of two subunits of unequal size, each carrying specialized functions in translation.
Translation is a key step in gene expression that converts the genetic information encoded in nucleic acids into proteins.
We are focusing our attention on ribosome synthesis in eukaryotes.
Eukaryotic cells are compartmentalized in several functional domains that are more or less separated physically. Although ribosome synthesis involves most cellular compartments, many of the initial steps occur in a specialized nuclear domain, the nucleolus. Recently, the nucleolus has attracted much attention as it turned out that this organelle is not only required for ribosome synthesis but is also involved in functions as diverse and essential as cell-cycle regulation, chromosome-ends maintenance, protein secretion, … in fact, most classes of cellular RNAs - and several viral RNAs - transit through the nucleolus.
Several projects in the Lab address nucleolar structure and morphogenesis. In 2005, we found out that, unlike previously assumed in the field for the last 30 years, most eukaryotes have only two subnucleolar compartments; the emergence of a third nucleolar compartment, we showed, is a recent evolutionary acquisition that coincides with the transition between the anamniotes and the amniotes (these include the lizards, birds and mammals)
Ribosome biogenesis is a complex process involving countless reactions, including steps of RNA synthesis, RNA processing, RNA modification, RNP assembly and RNP transport. These reactions require a couple of hundreds of snoRNAs (Small NucleOlar RNAs) and about as much protein trans-acting factors (collectively referred to as RRPs for Ribosomal Rna Processing factors). We have been deeply involved in the functional characterization of the snoRNAs and the RRPs.