Constitutive heterochromatin formation and transcription in mammals
Nehmé Saksouk†, Elisabeth Simboeck† and Jérôme Déjardin*
* Corresponding author: Jérôme Déjardin
jerome.dejardin@igh.cnrs.fr
† Equal contributors
INSERM AVENIR Team, Institute of Human Genetics, CNRS UPR 1142, Montpellier, France
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Epigenetics & Chromatin 2015, 8:3 doi:10.1186/1756-8935-8-3
Received: 28 October 2014
Accepted: 16 December 2014
Published: 15 January 2015
© 2015 Saksouk et al.; licensee BioMed Central.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Source/Fonte: Nature Reviews Molecular Cell Biology
Abstract
Constitutive heterochromatin, mainly formed at the gene-poor regions of pericentromeres, is believed to ensure a condensed and transcriptionally inert chromatin conformation. Pericentromeres consist of repetitive tandem satellite repeats and are crucial chromosomal elements that are responsible for accurate chromosome segregation in mitosis. The repeat sequences are not conserved and can greatly vary between different organisms, suggesting that pericentromeric functions might be controlled epigenetically. In this review, we will discuss how constitutive heterochromatin is formed and maintained at pericentromeres in order to ensure their integrity. We will describe the biogenesis and the function of main epigenetic pathways that are involved and how they are interconnected. Interestingly, recent findings suggest that alternative pathways could substitute for well-established pathways when disrupted, suggesting that constitutive heterochromatin harbors much more plasticity than previously assumed. In addition, despite of the heterochromatic nature of pericentromeres, there is increasing evidence for active and regulated transcription at these loci, in a multitude of organisms and under various biological contexts. Thus, in the second part of this review, we will address this relatively new aspect and discuss putative functions of pericentromeric expression.
Keywords: epigenetic factors; heterochromatin; histone modifying enzymes; pericentromere; transcription
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