Heterogeneous nuclear ribonucleoprotein A2-dependent mRNA trafficking in the cytoplasm of cells.

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Control of the use of DNA, gene expression, is vital to all living organisms, especially in development and disease. The information in the genes of DNA is transferred to an intermediate molecule, mRNA, in a process called transcription. The genetic information in the mRNA is subsequently used to make the protein encoded by the original gene. The switching on and off of DNA appears to be most frequently controlled at the transcription step but recently it has become apparent that there are many post-transcriptional events that govern how efficiently the genetic information is ultimately converted to protein molecules. The RNA molecules may be confined to a small region of the cell, resulting in the localization of the protein produced from it; the RNA may be rapidly degraded or stabilized; and the efficiency of production of the protein from its RNA precursor may be modulated by other molecules. It had previously been shown that the mRNA encoding a protein that is an essential structural component of central nervous system myelin is selectively transported to the regions in the cell where the myelin is made. We have identified the molecule that recognises this RNA as a protein called hnRNP A2 and shown how it selects the RNA molecules that have to be transported from the myriad of RNA moleclues in the cell at any given time. hnRNP A2 was previously thought to be confined to the nuclei of cells, but we have shown that it is also present outside the nucleus and is involved in RNA transport in a variety of cell types. hnRNP A2 appears to be directly involved in rheumatoid arthritis, lung cancer and other cancers. It has been proposed as a diagnostic test for cancer as elevated intracellular levels and circulating antibodies against this protein appear before the cancerous cells are visible under the microscope. The major aim of the proposed project is to explore the molecular mechanism by which hnRNP A2 transports RNA molecules in cells.