This is an ingenious mechanism which prevents transposons from increasing and killing us. The process is very simple, but it explains so much.
-Karen Lipkow
The study reveals for the first time how the movement and duplication of segments of DNA known as transposons is regulated. This prevents a genomic meltdown, and instead enables transposons to live in harmony with their hosts – including humans.
Transposons were discovered in the 1940s by Barbara McClintock, who was rewarded in 1983 with the Nobel Prize for Physiology or Medicine. Ancient relics of these "jumping genes", as they are sometimes called, make up 50% of the DNA in humans. They are characterised as “jumping” because they can change their position within the genome, thereby creating or reversing mutations. This process, known as DNA transposition, plays a critical role in creating genetic diversity and enabling species to adapt and evolve.
Transposons don't just jump from one location to another; they usually leave behind a copy of themselves at their original location. Left unchecked, this would lead to an exponential increase in their numbers. Exponential growth is always unsustainable, and in the case of transposons they would quickly kill their host.
Because this doesn’t happen, clearly some form of regulation is taking place within the genome. For a long time, scientists have understood that an enzyme called transposase, which is critical to the whole transposition process, also apparently brings it under control.
How this actually occurs has, however, remained a mystery – until now. For the first time, the new study, carried out by researchers at the University of Cambridge, the University of Nottingham, and the Fred Hutchinson Cancer Centre in Seattle, successfully identified the mechanism through which DNA transposition is regulated.
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Image: Structure of the mariner transpososome.
Credit: Structure by Richardson et al., Cell, 2009. Figure by Karen Lipkow.
Reproduced courtesy of the University of Cambridge
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