The Question
Messenger RNAs (mRNA) were discovered in the mid-20th century as molecules that copy the genetic information from DNA in the cell nucleus and carry it to the cytoplasm for protein synthesis. Even today, mRNAs are depicted as simple, short linear chains of nucleotides. Yet, this is misleading, as it does not convey the considerable physical length of these nucleic acid polymers, their propensity to fold, and their existence within diverse and variable protein coatings.
Over the course of its life cycle, every mRNA within eukaryotic cells assembles a complex and dynamic protein coating. These supramolecular assemblies, called messenger ribonucleoproteins (mRNPs), protect the integrity of the mRNA, aid in transport and control the spatiotemporal translation into protein. This is especially important in neurons, in which the unique morphology requires that specific mRNAs travel to the most extreme ends of the cells, the axon terminals, for local translation at the synapses. This spatial choreography supplies the synaptic structures with the proteins needed to sustain the signal that directs activities such as proper brain development or storing memories. Despite their importance in gene expression processes, and in contrast to other classes of RNPs such as ribosomes and spliceosomes, the makeup and transformations of individual mRNPs remain a mystery.
“Understanding the architectural principles of mRNA particles will inform us how the fragile genetic information carrier, mRNA, can safely traverse the crowded and extensive cellular environment of neuronal cells, ensuring that precise protein synthesis occurs only upon reaching the correct location.”
—Elena Conti
The Approach
The research project Visualizing the Messenger: Deciphering the Architecture of Neuronal mRNA Particles at the Atomic Level aims to discern the structure and biochemical nature of mRNPs in the brain throughout the mRNA life cycle. Recent breakthroughs in ad hoc biochemical approaches pioneered by the Conti research group have minimized issues with mRNP fragility and variability, allowing for the isolation of endogenous intact mRNPs.
The project will employ genetic editing to enable strategic molecular cloning in a scalable platform with human induced pluripotent stem cells to extract and analyze large quantities of physiological assemblies in their entirety. The researchers will characterize the protein and mRNA content of selected mRNP targets and study their intra- and intermolecular interactions using mass spectrometry and RNA sequencing. The structural organization of the mRNPs will be determined through cryogenic electron microscopy and electron tomography, aided by computational approaches. Elucidating the structure of these mRNPs will provide insights into the mechanisms with which they function in neuronal processes and will facilitate a molecular understanding of how mutations in mRNP components lead to neurological diseases.
The Visualizing the Messenger project is being led by Elena Conti at the Max Planck Institute of Biochemistry (MPIB) in Munich, Germany.
Feature image: Structural basis for the assembly and recognition of modules in mRNA ribonucleoproteins (mRNPs).
