Project Details
Projekt
Characterization of factors and mechanisms of starvation-induced control of TOP mRNA translation
Applicants
Professor Dr. Utz Fischer; Professor Dr. Jörg Vogel
Subject Area
General Genetics and Functional Genome Biology
Biochemistry
Cell Biology
Biochemistry
Cell Biology
Term
from 2016 to 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 313643704
A major task of dividing cells is the synthesis and maintenance of components of the translation apparatus, including ribosomal proteins, translation factors and mRNP associated proteins. As this process consumes a large proportion of available metabolic energy, it is tightly regulated in response to mitogenic and nutritional signals. In mammalian cells, this regulation occurs on the post-transcriptional level and is directed to mRNAs encoding the protein components of the translation machinery. These mRNAs contain a unique regulatory sequence element in cis, termed the 5' Terminal OligoPyrimidine (TOP) motif, which is the binding site for the translational repressor protein Larp1. In quiescent or starving cells, Larp1 is recruited to the TOP motif in an mTORC1 dependent manner, causing the formation of stable sub-polysomal mRNPs. Importantly, this event is reversible and allows re-establishment of the normal translation mode when metabolic conditions improve. While Larp1 is now well-established as one key factor in TOP mRNA regulation, little is known about the functional status of TOP mRNPs under starvation conditions, their biochemical composition and how they escape degradation. During the first funding period of this SPP, we have established the Grad-seq technique for mammalian cells and shown that Grad-seq enables a global investigation of TOP mRNP regulation in cellular extracts. Contrasting previous reports that concluded that TOP mRNPs are withdrawn from the translation machinery upon starvation, our Grad-seq and ribosome profiling results argue that TOP mRNPs adopt a new baseline translation mode. This unusual translation mode is not observed for canonical (non-TOP) mRNAs and is most likely caused by drastically reduced initiation rates. In the next funding period we will build on these findings to a) biochemically characterize the starvation-induced TOP-mRNP, b) functionally characterize factors that act in the TOP response and investigate how the baseline translation mode is achieved and maintained during starvation and c) identify how the normal translation mode is re-established upon return to normal growth conditions.
DFG Programme
Priority Programmes
