A compendium of the histone H1 family of somatic subtypes: an elusive cast of characters and their characteristics.

The last 35 years has seen a substantial amount of information collected about the somatic H1 subtypes, yet much of this work has been overshadowed by research into highly divergent isoforms of H1, such as H5. Reports from several laboratories in the past few years have begun to call into question some of the traditional views regarding the general function of linker histones and their heterogeneity. Hence, the impression in some circles is that less is known about these ubiquitous nuclear proteins as compared with the core histones. The goal of the following review is to acquaint the reader with the ubiquitous somatic Hls by categorizing them and their characteristics into several classes. The reasons for our current state of misunderstanding is put into a historical context along with recent controversies centering on the role of H1 in the nucleus. Finally, we propose a model that may explain the functional role of H1 heterogeneity in chromatin compaction.