Abstract
Besides chemical modification of histone proteins, chromatin dynamics can be modulated by histone variants. Most organisms possess multiple genes encoding for core histone proteins, which are highly similar in amino acid sequence. The Arabidopsis thaliana genome contains 11 genes encoding for histone H2B (HTBs), 13 for H2A (HTAs), 15 for H3 (HTRs), and 8 genes encoding for histone H4 (HFOs). The finding that histone variants may be expressed in specific tissues and/or during specific developmental stages, often displaying specific nuclear localization and involvement in specific nuclear processes suggests that histone variants have evolved to carry out specific functions in regulating chromatin structure and function and might be important for better understanding of growth and development and particularly the response to stress. In this review, we will elaborate on a group of core histone proteins in Arabidopsis, namely histone H2B, summarize existing data, and illuminate the potential function of H2B variants in regulating chromatin structure and function in Arabidopsis thaliana.
Highlights
IntroductionThe basic structural unit of chromatin is the nucleosome, which is composed of DNA wrapped around histone octamer made of two of each of the core histone proteins, namely, H2A, H2B, H3, and H4
The basic structural unit of chromatin is the nucleosome, which is composed of DNA wrapped around histone octamer made of two of each of the core histone proteins, namely, H2A, H2B, H3, and H4.These histone proteins share a structural motif, the histone fold [1] that mediates the interactions between core histone proteins and between histone octamer and duplex DNA
While class I HTBs carry a major function in regulating chromatin dynamics during growth and development of vegetative tissues, class II/III HTBs play a key role in controlling chromatin structure and function in reproductive tissues
Summary
The basic structural unit of chromatin is the nucleosome, which is composed of DNA wrapped around histone octamer made of two of each of the core histone proteins, namely, H2A, H2B, H3, and H4. The structure of chromatin is highly dynamic, enabling the transition between permissive (euchromatic) and repressive (heterochromatic) chromatin This dynamic structure is controlled by multiple types of reversible chemical modifications that occur on the DNA (mainly cytosine methylation) or on the core histone proteins (e.g., acetylation, methylation, ubiquitination). These chemical modifications can directly affect the interaction of histones with DNA or generate binding sites for the recruitment of proteins or protein complexes that affect the structure and function of chromatin and, differentiation and development as well as response to stress [2]. H3 and H2A variants [3,11,12,13,14], the study of histone H2B variants is emerging [15,16], and this topic represents the focus of the present review
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