How does histone modification affect chromatin structure?

Histone modifications regulate the physical properties of chromatin and its associated transcriptional state. This can be done either directly where acetyl groups repel negatively charged DNA to form open chromatin conformation; or  it can be done through protein adaptors. Histone acetylation and phosphorylation reduce the positive charge of histones and have the ability to directly interfere with the electrostatic interactions between DNA and histones. This leads to a less compact chromatin structure allowing DNA access. Direct modifications influence the overall structure of chromatin either over short or long distances. Effector proteins recognize and bind to specific epigenetic marks to alter chromatin structure. Epigenetic readers determine the outcome of histone modifications by translating the histone code.