English: Chromatin structure and binding proteins can affect transcription through multiple avenues.

Chemical additions can be made to histones by chromatin-modifying enzymes such as Set1, which adds methyl groups to a specific place on the histone (1); many of these chemical modifications can be removed by other proteins (2). Some proteins bind to specific modifications on histones that have been added (3). Nucleosome spacing (4) can be altered by chromatin remodelers that use the power of ATP to drive movement and histone chaperones (5) can remove and replace histones on DNA. All of these factors can control access of the DNA and chromatin to other factors, such as transcription factors that may need to bind open pieces of DNA (6). This is a dynamic process requiring many proteins to act in concert as appropriate.

doi:10.1371/journal.pbio.1001371.g002