Biology subjects

Bourgeois, G.

Publications and source records attributed to Bourgeois, G..

2 recordsLinked to original sources

bioRxiv2023

The YTHDF1-3 proteins are bidirectionally influenced by the codon content of their mRNA targets

N6-methyladenosine (m6A) is the most abundant modification in eukaryotic mRNAs and plays critical roles in a broad variety of biological processes. Recognition of m6A by the YTHDF1-3 proteins results in the alteration of the translation efficiency and stability of methylated mRNAs, although their mode of action is still matter of debates. To decode the molecular basis of YTHDF1-3 action in human cells, we performed an unbiased proteomic screen of their full spectrum of interacting proteins using BioID (proximity-dependent biotin identification). Our systematic BioID mapping revealed that each YTHDF protein is a dynamic hub that associates with both mRNA silencing machineries and the translation apparatus. Based on this, we identified a direct interaction between YTHDF2 and the ribosomal protein RACK1, and found that the silencing activity of YTHDF2 is bidirectionally modulated by the codon content of its targeted mRNAs. Using a tethering reporter system that recapitulates this phenomenon, we confirmed that the three YTHDF proteins selectively repress mRNAs enriched in optimal codons, while they activate those enriched in non-optimal codons. Altogether, these results have important implications for understanding the underlying multiplicity of YTHDF1-3 and could reconcile seemingly contradictory data.

cell biology↗

bioRxiv2022

Role of aIF5B in archaeal translation initiation

In eukaryotes and in archaea late steps of translation initiation involve the two initiation factors e/aIF5B and e/aIF1A. In eukaryotes, the role of eIF5B in ribosomal subunit joining is established and structural data showing eIF5B bound to the full ribosome were obtained. To achieve its function, eIF5B collaborates with eIF1A. However, structural data illustrating how these two factors interact on the small ribosomal subunit have long been awaited. The role of the archaeal counterparts, aIF5B and aIF1A, remains to be extensively addressed. Here, we study the late steps of Pyrococcus abyssi translation initiation. Using in vitro reconstituted initiation complexes and light scattering, we show that aIF5B bound to GTP accelerates subunit joining without the need for GTP hydrolysis. We report the crystallographic structures of aIF5B bound to GDP and GTP and analyze domain movements associated to these two nucleotide states. Finally, we present the cryo-EM structure of an initiation complex containing 30S bound to mRNA, Met-tRNAiMet, aIF5B and aIF1A at 2.7 [A] resolution. Structural data shows how archaeal 5B and 1A factors cooperate to induce a conformation of the initiator tRNA favorable to subunit joining. Archaeal and eukaryotic features of late steps of translation initiation are discussed.

biochemistry↗