Abstract

Chromatin remodeling complexes (CRCs) use ATP hydrolysis to maintain correct expression profiles, chromatin stability, and inherited epigenetic states. More than 20 CRCs have been described to date, which encompass four large families defined by their ATPase subunits. These complexes and their subunits are conserved from yeast to humans through evolution. Their activities depend on their catalytic subunits which through ATP hydrolysis provide the energy necessary to fulfill cellular functions such as gene transcription, DNA repair, and transposon silencing. These activities take place at the first levels of chromatin compaction, and CRCs have been recognized as essential elements of chromatin dynamics. Recent studies have demonstrated an important role for these complexes in the maintenance of higher order chromatin structure. In this review, we present an overview of the organization of the genome within the cell nucleus, the different levels of chromatin compaction, and importance of the architectural proteins, and discuss the role of CRCs and how their functions contribute to the dynamics of the 3D genome organization.

Highlights

  • Reviewed by: Nataliya Soshnikova, Institute of Gene Biology (RAS), Russia Giovanni Messina, Sapienza University of Rome, Italy

  • We present an overview of the organization of the genome within the cell nucleus, the different levels of chromatin compaction, and importance of the architectural proteins, and discuss the role of Chromatin remodeling complexes (CRCs) and how their functions contribute to the dynamics of the 3D genome organization

  • These data arise the question if in organisms like Drosophila or plants, where the orthologs of CCCTC-binding factor (CTCF) do not seem to have an essential role at topologically associating domain (TAD) boundaries or where CTCF is totally absent, CRCs play an important role in directing architectural proteins to their target sites in order to control chromatin looping and TAD formation

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Summary

CHROMATIN STRUCTURE AND ORGANIZATION

Eukaryotic DNA is compartmentalized into hierarchically organized levels within the nuclear space. At the first level of compaction, in an interphase chromosome, there exists a 6.5 nm diameter cylinder-like structure called nucleosome, which is formed by histone octamers with 146 base pairs (bp) of DNA wrapped around this core in 1.6 turns (Felsenfeld and Groudine, 2003; Bassett et al, 2009; McGinty and Tan, 2015; Pombo and Dillon, 2015) This tetramer is formed by two heterodimers of the histones H3 and H4, which are flanked by two heterodimers of H2A and H2B histones in a structure known as the “histone core.”. The number of nucleosomes per clutch is variable; they are interspersed with nucleosomedepleted regions, and the nucleosome density is cell-type specific (Ricci et al, 2015)

CHROMATIN LOOPS
CHROMATIN COMPARTMENTS
CHROMOSOME TERRITORIES
IS THE NUCLEAR ARCHITECTURE THE SAME IN ALL EUKARYOTIC ORGANISMS?
MODIFICATIONS IN THE CHROMATIN STRUCTURE
CHROMATIN REMODELING COMPLEXES
Promoter Clearance and CRC
CRC Association to Architectural Proteins
CRC in the Control of Compartments and TADs
CRC Association to Methyl CpG Binding Proteins
Findings
DISCUSSION

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