MOLECULAR BIOLOGY: Enzymes Display Intricacy in Repackaging DNA
For almost a half century, methylation of DNA-binding histones was thought to be irreversible. Two years ago, Yang Shi and colleagues discovered an enzyme that could remove a methyl group from histones bearing two such groups. Now, Johnathan Whetstine, Shi, Monica Colaiacovo (right to left), and colleagues report that they have uncovered a whole family of enzymes, capable in this case of stripping methyl groups not from dimethylated, but from the more heavily decorated, trimethylated, histones. The research appears in the May 5 Cell. In addition, they have completed a crystal structure of the active core of one of the enzymes, JMJD2A, which was published on May 4 in Cell online.

EPIGENETICS: Findings Get a Handle on Stemness
Research into epigenetics has shown how the structure of chromatin, the packed mass of DNA, histone and other proteins in the nucleus, carries information about which genes are on or off in a given cell. A study led by Bradley Bernstein (left) and Eric Lander, published in the April 21 Cell, shows that the chromatin of stem cells contains regions with characteristics of both active and repressed gene expression. These “bivalent domains” are found at key regulatory sites in the genome. The researchers believe these domains may be a structural correlate to stemness, a mechanism by which stem cells keep their plasticity.

NEUROSCIENCE: Seeing Guides Multiple Paths of Brain-shaping Growth
The question is no longer whether sensory experience shapes the brain, but how. Part of the answer lies in the nerve cells—in the form of activity-dependent genes. Carla Shatz (pictured) and Marta Majdan report in the May Nature Neuroscience that visual activity turns up and down the expression of different genes through a single enzyme and that during different stages of life in rodents, other distinct sets of genes spring into action in response to visual input. The findings show that “nurture, our experience of the world via our senses, acts through nature, sets of genes, to alter brain circuits,” said Shatz.