Fig. 1

The discovery of main features of chromatin organization

Diverse forms of chromatin organization have been identified ranging from the 100 bp scale to more than 100 Mb scale through a combination of different technologies over one century. The association between histone modification and gene transcription was identified through the incorporation of labeled chemical groups into histone structures in 1964 (Allfrey et al. 1964). DNA looping was first discovered using the helical-twist assay (Dunn et al. 1984). With the development of technologies, large chromatin interaction domains called topologically associating domains (TADs) and chromosome compartments indicating the spatial segregation of open and closed chromatin were identified with Hi-C (Dixon et al. 2012; Lieberman-Aiden et al. 2009). Thomas Cremer et al. carried out experiments using the laser to confirm the existence of chromosome territories which help to distinguish one chromosome from its neighbors (Cremer et al. 1982). In 1928, Emil Heitz improved cytological staining to define euchromatin and denser heterochromatin (Heitz 1928)