杏吧原创

THEORIES about how nature 鈥渟ilences鈥� genes have been challenged by the
discovery of a so-called Morpheus molecule. Named after the Greek god of sleep
and dreams, the molecule appears to be as important for sedating genes in plants
as methylation鈥攖he chemical process that was thought to be nature鈥檚
principal gene sedative.

Silencing ensures that certain genes aren鈥檛 expressed. With methylation,
enzymes add chemical units called methyl groups to specific genes. This was
thought to keep them quiet until the methyl groups were stripped off.

But while doing experiments on thale cress (Arabidopsis thaliana),
Jerzy Paszkowski, Yoshiki Habu and Paulo Amedeo of the Friedrich Miescher
Institute in Basle, Switzerland, managed to activate a silenced gene without
removing its methyl groups. The methylated gene was active only in plants that
lacked working versions of the Morpheus molecule. Once working versions were
reintroduced, the methylated gene was put back to sleep.

Adrian Bird, a geneticist at the University of Edinburgh, says he is not
surprised that alternative silencing mechanisms exist. But this is the first
time a silenced, methylated gene has been activated without being demethylated.
鈥淭hey鈥檝e got rid of the link between the two,鈥� he says.