Linker histone subtypes and their allelic variants

Abstract

Members of histone H1 family bind to nucleosomal and linker DNA to assist in stabilization of higher-order chromatin structures. Moreover, histone H1 is involved in regulation of a variety of cellular processes by interactions with cytosolic and nuclear proteins. Histone H1, composed of a series of subtypes encoded by distinct genes, is usually differentially expressed in specialized cells and frequently non-randomly distributed in different chromatin regions. Moreover, a role of specific histone H1 subtype might be also modulated by post-translational modifications and/or presence of polymorphic isoforms. While the significance of covalently modified histone H1 subtypes has been partially recognized, much less is known about the importance of histone H1 polymorphic variants identified in various plant and animal species, and human cells as well. Recent progress in elucidating amino acid composition-dependent functioning and interactions of the histone H1 with a variety of molecular partners indicates a potential role of histone H1 polymorphic variation in adopting specific protein conformations essential for chromatin function. The histone H1 allelic variants might affect chromatin in order to modulate gene expression underlying some physiological traits and, therefore could modify the course of diverse histone H1-dependent biological processes. This review focuses on the histone H1 allelic variability, and biochemical and genetic aspects of linker histone allelic isoforms to emphasize their likely biological relevance.

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

“…Among the remaining H1 histones in birds, the subtypes H1.a, H1.b, H1.c, H1.c' and H1.d were found as ubiquitous, contrary to the species-specific subtypes H1.a', H1.b' and H1.z (Kowalski and Pałyga, 2017). Whereas histone H1.c' has not been identified to date as polymorphic, the rest of the H1 subtypes show heterogeneity due to different abundance (i.e., protein band and/or spot intensity) and localization (i.e., disparate net charge or molecular weight) in the polyacrylamide gels (Kowalski and Pałyga, 2012a). The avian histone H1 polymorphic variants are variously distributed in the breeding (Górnicka-Michalska et al, 2014;Kowalski and Pałyga, 2014), conservative (Górnicka-Michalska et al, 2014;Kowalski and Pałyga, 2014) and wildliving (Kowalski et al, 2010Kowalski, 2016b) populations, which reflects their correlation with some of the phenotypic (Pałyga et al, 2000;Kowalski and Pałyga, 2014) and physiological (Pałyga, 1998a;Kowalski et al, 2015) organismal features.…”

“…It follows that the polymorphism of histone H1.a currently identified in the Japanese quail population resembles that which was already detected in chickens (Górnicka-Michalska et al, 2006) and duck (Kowalski et al, 1998) strains, and therefore it is distinct from a characteristic of the quail lines of the variety Pharaoh (Pałyga, 1998b). According to earlier reports (for a review, see Kowalski and Pałyga, 2012a), the histone H1 polymorphic variants are unequally distributed in the various avian populations, in which a considerably high frequency of one H1 phenotype with a simultaneous low frequency, or a lack, of the second phenotype was observed. Whereas a direct influence of histone H1 phenotypes on the organisms characteristics and functioning is unknown, it seems that the frequent histone H1 phenotype preferred in the population may evoke some breeding and/or physiologic effect, in contrast to the rare and/or missing phenotype.…”

A shift in erythrocyte histone H1 complement following selection in quail (Coturnix japonica)

“…Since histone H1 condensing function is mediated by a specific C-terminal domain amino acid composition (Hansen et al 2006;Lu et al 2009), the alterations in the C-terminal domain amino acid sequence (Kosterin et al 1994;Palyga et al 2000;Gornicka-Michalska et al 2006;Kowalski et al 2011a, b) seem to support functional diversity of these chromatin proteins. A specific role for the histone H1 allelic isoform might be assigned based on the cause and effect relationship between the appearance and/or disappearance of a given allele leading to the characteristic phenotypic effects (Kowalski and Palyga 2012a). The histone H1 allele frequencies were shown to correlate with growth dynamics (Kosterin et al 1994;Bogdanova et al 2007), accumulated temperature of vegetation period (Bogdanova et al 2005), and geographic distribution of plants (Berdnikov et al 1993;Dudnikov 2012), plumage colour in duck (Palyga et al 2000), and the effects of environmental pollution in hare (Lepus europaeus).…”

“…This indicates that C-terminal tail is a typical disordered domain, which in common with a disordered nature of N-terminal domain allows to classify H1 histones as highly disordered proteins (Peng et al 2012). Many histone H1 non-allelic subtypes may consist of allelic isoforms, thus the presence of allelic polymorphism is a distinctive feature of this histone class (Kowalski and Palyga 2012a). Since histone H1 allelic variants were shown to differ in the C-terminal domains (Palyga et al 2000;Berdnikov et al 2003;Sarg et al 2005;Gornicka-Michalska et al 2006;Bogdanova et al 2007;Villar-Garea and Imhof 2008;Kowalski et al 2011a), they could be able to interact with chromatin through the allele-specific effects as manifested by their fluctuated frequency in a given population (Palyga 1998a;Palyga et al 2000;Kowalski and Palyga 2014).…”

“…A functional diversification of histone H1 is linked with its heterogeneous composition reflected by the existence of several non-allelic subtypes in mammals (Parseghian and Hamkalo 2001;Happel and Doenecke 2009), birds (Shannon and Wells 1987;Palyga 1991), and plants (Berdnikov et al 1993, Kosterin et al 1994. Some histone H1 non-allelic subtypes play specialized functions (Kowalski and Palyga 2012a). For example, human histone H1.1 was shown to be essential for a proper activity of chromatinassociated protein, barrier to autointegration factor (BAF), involved in the integration of retroviral preintegration complexes (Montes de Oca et al 2005).…”