The epigenetic regulation of centromeres and telomeres in plants and animals

Abstract

<jats:p>The centromere is a chromosomal region where the kinetochore is formed, which is the attachment point of spindle fibers. Thus, it is responsible for the correct chromosome segregation during cell division. Telomeres protect chromosome ends against enzymatic degradation and fusions, and localize chromosomes in the cell nucleus. For this reason, centromeres and telomeres are parts of each linear chromosome that are necessary for their proper functioning. More and more research results show that the identity and functions of these chromosomal regions are epigenetically determined. Telomeres and centromeres are both usually described as highly condensed heterochromatin regions. However, the epigenetic nature of centromeres and telomeres is unique, as epigenetic modifications characteristic of both eu- and heterochromatin have been found in these areas. This specificity allows for the proper functioning of both regions, thereby affecting chromosome homeostasis. This review focuses on demonstrating the role of epigenetic mechanisms in the functioning of centromeres and telomeres in plants and animals.</jats:p>

Architecture and evolution of subtelomeres in the unicellular green algaChlamydomonas reinhardtii

“…While heterochromatin is thought to be a general property of subtelomeres in many organisms, chromatin organization at subtelomeres might be more complex ( 27 ) and for instance, its nature in plants is still a matter of debate ( 25 , 26 , 91 ). Here, we find that chromatin in C. reinhardtii might follow a simple organization.…”

Telomeres and Subtelomeres Dynamics in the Context of Early Chromosome Interactions During Meiosis and Their Implications in Plant Breeding

“…A general conclusion on the epigenetic state of telomeric chromatin is not possible since it is very dynamic and variable with the physiology of the organism. Epigenetic modifications are responsible for the regulation of telomere functioning (Procházková-Schrumpfová et al, 2019;Achrem et al, 2020).…”

Histone H1 protects telomeric repeats from H3K27me3 invasion inArabidopsis

“…The nature of plant ITR and telomere chromatin has long remained enigmatic (Achrem et al, 2020; Dvořáčková et al, 2015). Owing to their repetitive nature and to their sequence similarity with ITRs, telomeres are recalcitrant to sequencing-based technologies (Fojtová and Fajkus, 2014; Majerová et al, 2014; Vaquero-Sedas et al, 2011, 2012; Vega-Vaquero et al, 2016).…”

“…Owing to their repetitive nature (Fojtová and Fajkus, 2014; Majerová et al, 2014; Vaquero-Sedas et al, 2011, 2012; Vega-Vaquero et al, 2016), the chromatin composition and organization of plant telomeres has long remained enigmatic (Achrem et al, 2020; Dvořáčková et al, 2015). ChIP dot-blot analyses indicated a dominance of H3K9me2 over H3K27me3 histone marks but some of the Arabidopsis telomere regions also display euchromatic H3K4me2/3 marks (Adamusová et al, 2020; Grafi et al, 2007; Vaquero-Sedas et al, 2011).…”

“…Such a small DNA linker size (e.g., 5 bp) is seemingly incompatible with H1 ability to incorporate into chromatin, a process that protects about 20 bp of DNA in vitro (Simpson, 1978). Consistently, H1 has been proposed to be underrepresented at telomeres in plants (Ascenzi and Gantt, 1999;Fajkus et al, 1995) as in mammals (Achrem et al, 2020;Déjardin and Kingston, 2009;Galati et al, 2013;Makarov et al, 1993). This could explain the short NRL of Arabidopsis and human telomeres (Ascenzi and Gantt, 1999;Lejnine et al, 1995) and led to the interpretation that H1-free telomere chromatin segments could display a columnar structure in which nucleosome arrays are stabilized be stacking interactions mediated by the histone octamers themselves (Fajkus and Trifonov, 2001).…”