[Spatial organization of interphase chromosomes and the role of chromatin fiber dynamycs in the positioning of genome elements].

Many studies are devoted to the analysis ofinterphase chromosome architecture due to the evidence of functional-dependent spatial organization of the genome. These studies are based on classical cytological methods as well as on biochemical approaches (3C, 4C, 5C, Hi-C) allowing for the detection of long-range interactions between fragments of chromatin fibers, including the genome-wide interactions. In this review, we discuss the results of these researches which make it possible to explain functional-dependent multilevel compartmentalization of the nucleous and unravel the principals of high-level chromatin organization. Special attention is paid to the enchancer-promoter interactions important for the regulation of gene expression. Accordingly, we consider the model of an active chromatin hub and the alternative model of an active chromatin compartment, which was proposed based on reconsideration of some steps of the 3C procedure.

Domains of α- and ß-globin genes in the context of the structural-functional organization of the eukaryotic genome.

The eukaryotic cell genome has a multilevel regulatory system of gene expression that includes stages of preliminary activation of genes or of extended genomic regions (switching them to potentially active states) and stages of final activation of promoters and maintaining their active status in cells of a certain lineage. Current views on the regulatory systems of transcription in eukaryotes have been formed based on results of systematic studies on a limited number of model systems, in particular, on the α- and ß-globin gene domains of vertebrates. Unexpectedly, these genomic domains harboring genes responsible for the synthesis of different subunits of the same protein were found to have a fundamentally different organization inside chromatin. In this review, we analyze specific features of the organization of the α- and ß-globin gene domains in vertebrates, as well as principles of activities of the regulatory systems in these domains. In the final part of the review, we attempt to answer the question how the evolution of α- and ß-globin genes has led to segregation of these genes into two distinct types of chromatin domains situated on different chromosomes.