Structural and functional investigation of the SRSF1-mediated nuclear export of mRNAs

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Cells form the basic living units of the body, converting food and oxygen into energy to produce proteins that serve as building blocks and molecular machines. The DNA blueprint that contain genes for making up proteins is housed in a cell centre, the nucleus, which is separated from the surrounding compartment, the cytoplasm, where proteins are manufactured. Messenger intermediate molecules (mRNAs) copied from the blueprint are transported from the nucleus into the cytoplasm across nuclear openings where each mRNA guides the assembly of one type of protein. Other RNAs are also produced from the core DNA blueprint and require passage into the cytoplasm - they do not convey information for assembling the proteins but allow building some of the gene-working machineries and modulating the production of proteins depending on the needs of the cells. The quantity and functionality of tens of thousands of proteins account overall for the normal functioning or the death of cells. We and others have shown that the protein with the name SRSF1 has an important role in transporting mRNAs into the cytoplasm by bringing mRNAs into contact with another protein, NXF1, which drives mRNAs through the nuclear openings. In addition, we recently reported that the attachment of SRSF1 to differently shaped C9ORF72 mRNAs, involved in lethal diseases of the brain called amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), is also responsible for inducing transportation of these peculiar mRNAs into the cytoplasm. The precise mechanisms of how SRSF1 attaches to NXF1 and mRNAs for transport into the cytoplasm remain to be discovered. Our research project now aims to (i) understand precisely how SRSF1 attaches to the C9ORF72-ALS/FTD RNAs and NXF1 and (ii) how SRSF1 induces transportation of these RNAs into the cytoplasm. We will carry out experiments in human nerve cells and fruit fly models of C9ORF72-ALS/FTD as well as with combinations of pure SRSF1, NXF1 and RNA in test tubes. This will allow understanding for the first time how this dynamic process occurs at the scale of atoms. Our programme of research has three complementary objectives:1. Discover how SRSF1 attaches to NXF1 at the atomic level.2. Discover how SRSF1 attaches to two types of shaped C9ORF72-ALS/FTD RNAs forming special four-stranded or double-stranded structures at the atomic level.3. Examine how SRSF1, C9ORF72-ALS/FTD RNAs and NXF1 assemble at the microscopic level to form a single composite transport machine and how important this is for promoting the transport of RNAs into the cytoplasm of human cell models and C9ORF72-ALS/FTD nerve cells and fruit fly models.In the long term, we expect that a detailed understanding of the mechanisms by which SRSF1 allow transport of RNA though nuclear openings would have far-reaching implications for the understanding of novel biological mechanisms and the potential future development of drug inhibitors for the treatment of some neurodegenerative diseases such as C9ORF72-ALS/FTD. Several communities of academic researchers including students and scientists will directly be involved in conducting the research. Furthermore, this work will lead to inspirational communications, presentations and publications that will benefit the academic community, the general public, local schools, the tertiary sector and potentially in the longer term the biotechnology sector and the pharmaceutical industry.