Academic journal article Genetics

Control of Maize Vegetative and Reproductive Development, Fertility, and rRNAs Silencing by HISTONE DEACETYLASE 108

Academic journal article Genetics

Control of Maize Vegetative and Reproductive Development, Fertility, and rRNAs Silencing by HISTONE DEACETYLASE 108

Article excerpt

HISTONE acetyltransferases (HATs) and histone deacetylases (HDAs) are the enzymes required to perform histone acetylation and deacetylation, respectively. Acetylation, together with other covalent modifications of the histone N-terminal tails in nucleosomes, plays important roles in chromatin assembly. Acetylation of conserved lysine residues in the N-terminal tails of histones neutralizes their positive charge, decreasing histone affinity for negatively charged DNA and resulting in chromatin conformation and gene promoter accessibility changes. As a general rule, hyper-acetylated histones are associated with gene activation, while hypoacetylated histones are related to gene repression. HDAs interact with various corepressors in different large multiprotein chromatin modifying complexes (Mehdi et al. 2016; Perrella et al. 2016). However, some reports have shown that HDAC complexes are involved in both repression and activation of transcription in yeast as well as in human cells (Wang et al. 2002; Z. Wang et al. 2009; Greer et al. 2015; Jian et al. 2017). Histone modification patterns are also thought to generate a "histone code" that provides signals for the recruitment of specific protein complexes, which alter chromatin states and affect transcription (Jenuwein and Allis 2001).

HDAs are grouped into three families based on their similarity to known yeast histone deacetylases (Pandey et al. 2002); the first family of HDAs includes proteins that carry homology to the yeast RPD3 (Reduced Potassium Deficiency 3) and HDA1 (Histone Deacetylase 1) proteins, which are present in all eukaryotes. The second family comprises the plant-specific HD-tuins, the first member of which was identified in maize (Lusser et al. 1997), whereas the third contains proteins that are homologous to the Sir2 (Silent Information Regulator Protein 2) NAD-dependent proteins.

In plants, the RPD3/HDA1 family is further divided into three distinct groups: class I, class II, and class IV (Alinsug etal. 2009; Aiese Cigliano et al. 2013). In Arabidopsis there are six genes that belong to class I of the RPD3/HDAI family, including HDA19 and HDA6, which share similar expression profiles and biological processes (Hollender and Liu 2008). HDA19 acts as a global transcriptional regulator in response to changes in developmental programs, physiological processes, and pathogen response (Tian et al. 2005; Zhou et al. 2005). In transgenic Arabidopsis plants, the up- and down-regulation of HDA19 was associated with histone H4 hypoacetylation and hyper-acetylation, respectively (Tian and Chen 2001; Tian et al. 2005; Zhou et al. 2005).

The Arabidopsis HDA6 is responsible for the silencing of transgenes, transposable elements, and ribosomal RNA, as demonstrated through the characterization of several hda6 mutant alleles (Murfett et al. 2001; Aufsatz et al. 2002; Lippman et al. 2003; Probst et al. 2004). HDA6 is also required for inactivation of Nuclear Organizing Regions in Arabidopsis (NORs; Earley et al. 2006) and is a crucial player in Arabidopsis growth and development: it can interact with ASYMETRIC LEAVES1 MYB domain proteins in vivo and in vitro, being part of the AS1 repression complex that regulates the expression of KNOX genes in leaf primordia (Luo et al. 2012). Identification and characterization of the epigenetic control1 (epic1) Arabidopsis HDA6 mutant allele (renamed hda6-8) led to the conclusion that this histone deacetylase has independent euchromatic and heterochromatic functions and may inhibit de novo DNA methylation in the CG sequence context (Hristova et al. 2015). The characterization of two further mutant alleles, namely hda6-9 and hda6-10, confirmed that mutations in different domains of the HDA6 protein may have different impact on DNA methylation and histone modifications (Zhang et al. 2015). Very recently, it has been reported that HDA6 can deacetylate BIN2 to repress kinase activity and enhance brassinosteroids signaling in Arabidopsis (Hao et al. …

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