The H1 linker histones: multifunctional proteins beyond the nucleosomal core particle

Abstract

The linker histone H1 family members are a key component of chromatin and bind to the nucleosomal core particle around the DNA entry and exit sites. H1 can stabilize both nucleosome structure and higher-order chromatin architecture. In general, H1 molecules consist of a central globular domain with more flexible tail regions at both their N-and C-terminal ends. The existence of multiple H1 subtypes and a large variety of posttranslational modifications brings about a considerable degree of complexity and makes studying this protein family challenging. Here, we review recent progress in understanding the function of linker histones and their subtypes beyond their role as merely structural chromatin components. We summarize current findings on the role of H1 in heterochromatin formation, transcriptional regulation and embryogenesis with a focus on H1 subtypes and their specific modifications.

Yeast HMO1: Linker Histone Reinvented

“…Interactions between nucleosomes promote the folding of the nucleosomal array into a more compact 30-nm fiber, for example, by the interaction of the H4 N-terminal tail with an acidic patch formed at the H2A/H2B interface on a neighboring nucleosome (11). The linker histone H1 plays an indispensable role in stabilizing the 30-nm fiber in which nucleosomes are clustered tightly together, decreasing the internucleosomal distance and fixing the entry/exit angle of DNA (12)(13)(14)(15)(16). This compaction is affected by the nucleosomal repeat length, as the repeat length must be sufficient to accommodate H1 binding; for nucleosomal arrays with shorter repeat lengths, internucleosome interactions drive the folding of a more compact fiber that is less affected by linker histone binding (17).…”

“…Some are constitutively expressed in all cells, while others are developmentally regulated, restricted to specific cell types, or induced at certain stages of differentiation. Covalent modifications contribute further to functional diversity (14)(15)(16)47). Although the sequence of the winged-helix motif is relatively well conserved, the CTDs are extremely variable in both length and amino acid composition.…”

The Histone Deacetylase Complex 1 Protein of Arabidopsis Has the Capacity to Interact with Multiple Proteins Including Histone 3-Binding Proteins and Histone 1 Variants

“…Transcription occurs in the context of chromatin, a highly condensed structure in which the DNA is wrapped around nucleosomes composed of histones H2A/B, H3, and H4 and further stabilized by linker histone H1 (Over and Michaels, 2014;Hergeth and Schneider, 2015). Alteration of chromatin structure plays an important part in transcriptional regulation and is achieved through multiprotein complexes that recognize and instigate biochemical modifications of the DNA and/or the histones (Pfluger and Wagner, 2007;Derkacheva et al, 2013).…”

Evidence on the stability of histone H1.a polymorphic variants during selection in quail

“…Despite the mechanism of avian histone H1 subtypes being obscure, their mode of action might be similar to the mammalian H1 subtypes. Their common and individual activity, related to DNA and protein interaction as well as to the regulation of gene expression, manifests differently in peculiar cellular processes (for a review, see Herghet and Schneider, 2015;Kalashnikova et al, 2016;Kowalski and Pałyga, 2016a;Parseghian, 2015). Therefore, the function of certain avian H1 subtypes (H1.b, H1.d and H1.z) displaying altered allele frequency in response to selection (Kowalski et al, 2015) might be associated with genetic and/or epigenetic regulation of egg yolk cholesterol content, in contrast to the subtype H1.a, whose phenotypic variants were detected in this work as similarly frequent, irrespective of conducted selection.…”

“…Due to the presence of the arginine residues, the sperm H1-like histones are able to form aggregates and highly condensed DNA in comparison to the somatic H1 histones deprived of arginine and are thus unable to selfassociate and create highly packaged DNA (Salvati et al, 2008). Therefore, histone H1 influences gene expression, regulating the access of transcription factors to the target DNA sequences (Herghet and Schneider, 2015). As a consequence, histone H1 is engaged in a range of activities, including cell cycle regulation and cellular response as well as repair of damaged DNA and transmission of the apoptotic signals (Roque et al, 2016).…”