In the August 10 issue of Science, Cold Spring Harbor Laboratory researcher Shiv Grewal and his colleagues report that seemingly small differences between two varieties of histone have dramatic effects on chromosome structure and gene expression. They found that "silent" regions of chromosomeswhere genes are kept "off" and DNA resists genetic recombinationcontain one variety of histone H3. In contrast, the researchers found that "active" regions of chromosomeswhere genes can be easily switched "on" and DNA can readily recombinecontain a slightly different variety of histone H3. Histone H3 in silent DNA had a "methyl" group attached to a particular lysine amino acid, #9. Histone H3 in active DNA had a methyl group attached to a different, nearby lysine amino acid, #4. (color illustration available)
Interestingly, Grewal and his colleagues showed that deleting "boundary elements" which mark the transition between silent and active regions of DNA allowed the spreading of lysine 9-methylated histones into neighboring DNA normally occupied by lysine 4-methylated hi
Contact: Peter W. Sherwood, Ph.D.
Cold Spring Harbor Laboratory