Dynamic chromatin. Chromatin consists of arrays of nucleosomes (N) with a number of dynamic features such as nucleosome position, histone-variant composition of nucleosomes, post-translational modifications of histones, as well as the binding of transcription factors, chromatin-remodeling complexes, and modification binding proteins. Transcription factors (TFs) and remodeling complexes (R) are in equilibrium between the bound and unbound states, and nucleosomes can slide along DNA, be dislodged from DNA, and be reassembled. In addition, a wide variety of histone modifications (m) can be added and removed enzymatically. The right-angled arrow indicates the transcription start site.