CLONING researchers have found an enzyme that appears to be essential to an
egg鈥檚 surprising ability to genetically 鈥渞eprogram鈥� the nuclei of adult
cells.
When an adult nucleus is inserted into an unfertilised egg, it somehow
regains its ability to act like the DNA in an early embryo. Now, using cell
nuclei and egg extracts from frogs, Alan Wolffe of Sangamo BioSciences in
Richmond, California, and his colleagues have shown that an egg enzyme called
ISWI removes a key protein that binds to DNA.
This protein normally helps stabilise the 鈥減ackaging鈥� of the long strands of
DNA in a nucleus, and erasing it may open up DNA to further remodelling
(Science, vol 289, p 2360).
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