How to Read the Chromatin Past

摘要

It has become common parlance to refer to all histone modifications as "epigenetic," meaning that they carry information about how to use the associated DNA sequences as a function of earlier events. However, some histone modifications, such as methyla-tion of histone H3 at lysine 27 (H3K27), are more epigenetic than others in that they can self-renew from one cell cycle to the next, thereby establishing a "cellular memory" of earlier events.