Our laboratory is interested in uncovering the link between environmental signals (e.g., viruses and phytohormones), fundamental cellular processes such as protein synthesis, plant growth and organogenesis. A central signaling molecule that correlates growth with nutrients and energy sufficiency is the target of rapamycin (TOR). TOR is a major controller of translation initiation in mammals and yeast.
In eukaryotes, protein production is limited by upstream open reading frames (uORFs) located within the 5’UTRs of about 30% of eukaryotic mRNAs encoding highly potent regulatory proteins (e.g. growth factors, protein kinases, and transcription factors). Translation of uORF-containing mRNAs (uORF-mRNAs) depends on a reinitiation mechanism, where ribosomes terminating translation of a uORF resume scanning and reinitiate at an ORF further downstream on the same mRNA. Although mechanisms of translation reinitiation are not well understood, subunit h of eukaryotic translation initiation factor 3 (eIF3), if phosphorylated by the TOR signalling pathway, was shown to be a critical essential reinitiation factor.
In plants, we have established that TOR perceives growth hormone auxin through a small GTPase ROP2 that directly binds and activates TOR and thereby promotes translation reinitiation and plant growth. Currently, the auxin–ROP2–TOR signaling axis represents the most well studied example of upstream TOR regulation.
Our team works on novel TOR upstream effectors and downstream targets studying their role in reinitiation and cap-dependent initiation of translation in plants. Cauliflower mosaic virus (CaMV) employs an unique strategy to translate viral polycistronic 35S RNA by using the reinitiation mechanism. To understand mechanisms of reinitiation after uORF translation, we study how a CaMV translational transactivator/ viroplasmin (TAV) overcomes cellular barriers to reinitiation after long ORF translation.
Our research programs are supported by international (Marie-Curie fellowships) and national (ANR) programmes.
