Nuclear and nucleolar activity of linker histone variant H1.0.

Andrzej Kowalski

doi:10.1186/s11658-016-0014-0

Abstract

Histone H1.0 belongs to the class of linker histones (H1), although it is substantially distinct from other histone H1 family members. The differences can be observed in the chromosomal location and organization of the histone H1.0 encoding gene, as well as in the length and composition of its amino acid chain. Whereas somatic (H1.1–H1.5) histone H1 variants are synthesized in the cell cycle S-phase, histone H1.0 is synthesized throughout the cell cycle. By replacing somatic H1 variants during cell maturation, histone H1.0 is gradually deposited in low dividing cells and achieves the highest level of expression in the terminally differentiated cells. Compared to other differentiation-specific H1 histone (H5) characteristic for unique tissue and organisms, the distribution of histone H1.0 remains non-specific. Classic investigations emphasize that histone H1.0 is engaged in the organization of nuclear chromatin accounting for formation and maintenance of its nucleosomal and higher-order structure, and thus influences gene expression. However, the recent data confirmed histone H1.0 peculiar localization in the nucleolus and unexpectedly revealed its potential for regulation of nucleolar, RNA-dependent, activity via interaction with other proteins. According to such findings, histone H1.0 participates in the formation of gene-coded information through its control at both transcriptional and translational levels. In order to reappraise the biological significance of histone H1.0, both aspects of its activity are presented in this review.

Highlights

The majority of histone H1 subtypes, including those that are specific of sperm (H1t, H1T2, and H1LS1) or oocytes (H1oo) as well as those active in the somatic cells (H1.1–H1.5 and H1X), can be characterized as having more than 200 amino acids in chain [1], with the largest share of the Ala and Lys residues
While genes encoding human somatic H1 histones are usually clustered on the short arm of chromosome 6, and their non-polyadenylated mRNAs contains hairpin loop terminal element, the histone H1.0 encoding gene is separately located on the long arm of chromosome 22, and its polyadenylated mRNA comprises an extended 3′ noncoding segment [6]
Histone H1.0 is known as differentiation-specific histone H1 variant, which may be found in many vertebrates, mainly in mammals [8, 9] and amphibians [10], and in fish [11] and reptiles [12]

Summary

Introduction

The majority of histone H1 subtypes, including those that are specific of sperm (H1t, H1T2, and H1LS1) or oocytes (H1oo) as well as those active in the somatic cells (H1.1–H1.5 and H1X), can be characterized as having more than 200 amino acids in chain [1], with the largest share of the Ala and Lys residues. A partial redundancy is linked to the histone H1 function [25], a large number of recent studies indicate the individual impact of histone H1 subtypes on DNA binding and chromatin compaction related to the regulation of gene expression [1, 24, 30, 32].

Results

Conclusion