Abstract
The regulation of gene expression has been studied for decades, but the underlying mechanisms are still not fully understood. As well as local and distant regulation, there are specific mechanisms of regulation during development and physiological modulation of gene activity in differentiated cells. Current research strongly supports a role for the 3D chromosomal structure in the regulation of gene expression. However, it is not known whether the genome structure reflects the formation of active or repressed chromosomal domains or if these structures play a primary role in the regulation of gene expression. During early development, heterochromatinization of ribosomal DNA (rDNA) is coupled with silencing or activation of the expression of different sets of genes. Although the mechanisms behind this type of regulation are not known, rDNA clusters shape frequent inter-chromosomal contacts with a large group of genes controlling development. This review aims to shed light on the involvement of clusters of ribosomal genes in the global regulation of gene expression. We also discuss the possible role of RNA-mediated and phase-separation mechanisms in the global regulation of gene expression by nucleoli.
Highlights
Nucleoli are the largest organelles in nuclei
In the MYC-driven lymphoma model, during the cellular transition from premalignancy to malignancy, there is a correlation between interactions of associated genes with the ribosomal DNA (rDNA) and transcriptional repression. These results suggest that the interactions with nucleoli contribute to Pol II gene regulation during the development of malignancy (Diesch et al, 2019)
The abnormal function of nucleoli leads to cancer genesis and diseases
Summary
Nucleoli are the largest organelles in nuclei They are not separated from chromosomes by any kind of membrane and potentially could shape contacts with chromosomal regions in interphase cells either without any particular order, or in some order to attain structural or functional features. If ordered, these contacts should be re-established in the course of cell division and epigenetic mechanisms may be involved. The size of the attached chromosomal DNA fragments (up to 1 Mb) did not allow a precise estimation of the contact sites of nucleoli in chromosomes or to determine their roles
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