In a study that could change the way scientists view the process of protein production in humans, University of Chicago researchers have found a single gene that encodes two separate proteins from the same sequence of messenger RNA.
Published online July 3 in Cell, their finding elucidates a previously unknown mechanism in human gene expression and opens the door for new therapeutic strategies against a thus-far untreatable neurological disease.
"This is the first example of a mechanism in a higher organism in which one gene creates two proteins from the same mRNA transcript, simultaneously," said Christopher Gomez, MD, PHD, professor and chairman of the Department of Neurology at the University of Chicago, who led the study. "It represents a paradigm shift in our understanding of how genes ultimately encode proteins."
The human genome contains a similar number of protein-coding genes as the nematode worm (roughly 20,000). This disparity between biological complexity and gene count partially can be explained by the fact that individual genes can encode multiple protein variants via the production of different sequences of messenger RNA (mRNA)short, mass-produced copies of genetic code that guide the creation of myriad cellular machinery.
Gomez and his team, which included first author Xiaofei Du, MD, discovered a new layer of complexity in this process of gene expression as they studied spinocerebellar ataxia type-6 (SCA6), a neurodegenerative disease that causes patients to slowly lose coordination of their muscles and eventually their ability to speak and stand. Human genetic studies identified its cause as a mutation in CACNA1Aa gene that encodes a calcium channel protein important for nerve cell functionresulting in extra copies of the amino acid glutamine.
However, although the gene, mutation and dysfunction are known, attempts to find the biological mechanism of the disease proved inconclusive. Calcium
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University of Chicago Medical Center