“This will be remembered as the K4/K9 meeting,” remarked one participant at a recent Colorado gathering. The meeting covered all of chromatin biology, but talks kept returning to methyl modifications at lysine 4 (K4) and lysine 9 (K9) of histone H3. Methylation of K4 is associated with gene activation; methylation of K9 with gene repression.
The K4/K9 story is representative of a field that was, until recently, a backwater. Its rejuvenation can be traced to two innovations—a switch from purified to messy assay systems, and the isolation of antibodies that recognize modified histones. These innovations have allowed the identification of critical enzymes that modify histones by adding and removing moieties such as methyl and acetyl groups. Gene expression, in turn, is regulated by proteins that recognize the presence or absence of these modifications.
K4/K9 modifications have the highest profile at present, but they are not...
