tRNA ligase complex as a target of a new degradation pathway

Our genetic information is stored in the DNA and resembles a silent book. The way such information is read has been enunciated by the Nobel Prize Francis Crick in 1958 in the Sequence Hypothesis of Information Transfer: The residue-by-residue transfer of sequence information between biological macromolecules of three distinct classes: DNA, RNA, and protein. My laboratory, once at IMBA and now at the Max Perutz Labs and the Medical University of Vienna, has always investigated the biology of RNA, the middle component in Francis Cricks trilogy. However, we also study proteins and particularly active proteins, or enzymes, those that cut, join and modify RNA molecules to turn them functional. No RNA is worth unless precisely processed. This proposal is unique in the way it has originated, and it is also synergistic. A main part of it arose from a recently published, ground-breaking paper, describing a new mechanism to degrade cellular proteins based on their oxidation. The first author did his PhD at the IMP, in Vienna. The other part relies in what we have learnt over the years about the tRNA ligase complex (tRNA-LC), the enzyme that re-joins two half pieces of tRNAs once an internal sequence intron has been removed. The overlap between the two parts is that, the degradation mechanism primarily impacts the tRNA-LC. In other words, we knew many things about the tRNA-LC but ignored it could be specifically degraded by an oxidative mechanism. Here is where the synergism arises, because it will lead us to discover a completely new facet of the tRNA-LC. We will investigate how is the tRNA-LC degraded, which component of the complex it is composed of five proteins is initially targeted, where does it happen within the cell and which roles other proteins that are essential for the function of the tRNA-LC play in the degradation. In addition, the proposal contains two extra, exploratory research directions. The first is to investigate whether degradation is also driven by an enzyme that has never been linked to the processing of RNAs, but rather to the chemical modification of hormones to activate them. The enzyme is known as PAM, for peptidylglycine alpha-amidating monooxygenase. We link PAM to the degradation of the tRNA-LC based on an evolutionary analysis we conducted in the laboratory. The other high risk high gain direction is to turn the tRNA-LC immune or resistant to such degradative process. How? By mutagenizing it, changing it in a way that oxidation will not damage it anymore. As usual, our expertise will not suffice, and we will enjoy collaborating with experts in particular technologies, and among them with the laboratory that published the ground-breaking report. Preliminary data was obtained by Moritz Leitner and Sebastian Guzman Perez, both superb PhD students in my lab, and by Igor Asanovic, PostDoc, and a group of students he has skillfully supervised. Igor has massively contributed to the writing of the proposal. We expect great biology coming out from these studies!