DIVERSITY OF H2A HISTONES AND THEIR IMPLICATIONS FOR NUCLEOSOME STRUCTURAL PROPERTIES

Abstract

Histone proteins are key epigenetic factors, which play an important role in chromatin dynamics and gene activity regulation. They are divided into two broad classes: canonical histones and their variants. Canonical histones are expressed mainly during the S-phase of the cell cycle, as they are involved in DNA packaging during cell division. Histone variants are histone genes that are expressed and regulate chromatin dynamics throughout the cell cycle. Due to the functional and species diversity, various families of histone variants are distinguished. Some proteins may diff er slightly from canonical histones, while others, on the contrary, may have many important structural and functional features that aff ect nucleosome stability and chromatin dynamics. In order to assess the variability of the H2A histone family and their role in nucleosome structure, we performed a bioinformatic analysis of the amino acid sequences of the H2A histone family. The clustering performed by the UPGMA method made it possible to reveal two main subfamilies of H2A proteins: short H2A and other H2A variants demonstrating highly conserved amino acid sequences. We also constructed and analyzed multiple alignments for various H2A histone subfamilies. It is important to note that the proteins of the short H2A subfamily are not only the least conserved within the H2A family, but also have features that signifi cantly aff ect the structural properties of the nucleosome. In addition, we performed a phylogenetic analysis of short H2A, which resulted in the identifi cation and characterization of individual clades on the phylogenetic tree for the variants H2A.B, H2A.P, H2A.Q, H2A.L.