N-terminal histone

In addition to histone deacetylation, histone lysine methylation can also lead to gene silencing which is not blocked by the HDAC inhibitors [6, 51], Several lines of evidence have suggested a connection between cancer and histone lysine methyltrans-ferases (HKMTs) [52], HKMTs catalyze the transfer of methyl group(s) from the cofactor. S -adenosyI-methionine (AdoMet) to some specific lysine residues in the N-terminal histone tails [53, 54], With one exception of Dotl [55], all known HKMTs contain the SET domain which represents a novel structural fold [53, 56], Among SET-domain HKMTs, SET7/9 is one of the best characterized experimentally. It is a... 

Fig. 5. SFM images of chicken erythrocyte chromatin fibers. (A) Untrypsinized, linker histone-containing control fibers, and (B) linker histone-stripped fibers. The stripping of linker histones destroys both the three-dimensional interactions of adjacent nucleosomes and the zig-zag arrangement of consecutive nucleosomes. Trypsinization of the N-terminal histone tails of the linker histones and core histone H3 result in the loss of the three-dimensional association of the consecutive nucleosomes, but does not destroy the zig-zag configuration. Imaging of fibers deposited onto mica was performed in air under conditions of ambient humidity and temperature (from Ref. [32]). Full width of each image corresponds to 500 nm.

In cells of the mammary gland, either in normal epithelial or in cancerous cells, the packaging of chromosomal DNA into chromatin restricts the access of the transcription machinery, thereby causing transcriptional repression. The basic N-termini of histones are subject to post-translational modifications, including lysine acetylation, lysine and arginine methylation, serine phosphorylation and ubiquitinylation [56]. It has been proposed in the histone code hypothesis that the intricate pattern of modifications of the N-terminal histone tail influences gene regulation [57]. 

Add antibody specific for acetylated N-terminal histone tail... 

We turn now to histone lysine methyltransferase (HKMT) which catalyzes the methylation of the N-terminal histone tail of chromatin using the 5-adenosyl-methionine (SAM) cofactor as the methylating agent (see Fig. 1). 

Davis WB, Bjorklund CC, Dehne M. Probing the effects ofDNA-protein interactions on DNA hole transport the N-terminal histone tails modulate the distribution of oxidative damage and chemical lesions in the nudeosome core particle. Biochemistry. 2012 51 3129-3142. 

Histone phosphorylation is a common posttranslational modification fond in histones, primarily on the N-terminal tails. Phosphorylation sites include serine and threonine residues, tyrosine phosphorylation has not been observed so far. Some phosphorylation events occur locally whereas others occur globally throughout all chromosomes during specific events like mitosis. Histone phosphorylation is catalyzed by kinases. Removal of the phosphoryl groups is catalyzed by phosphatases. 

Histone tails are the N-terminal regions of histones which reach outside the nucleosomes. They are not essential for the formation in of nucleosomes but are required for the formation of higher-order chromatin structures. The histone tails are also known to be heavily posttranslationally modified by acetylation, phosphorylation, methylation, etc. and are important for the regulation of gene activity. 

The histone variants of H2A form the largest family of identified histone variants (Redon et al, 2002 Sarma and Reinberg, 2005). This could be associated with both the strategic position that has the histone H2A within the histone octamer and the less stable interaction of the H2A-H2B dimmer with both DNA and the (H3-H4)2 tetramer within the nucleosome (Luger et al, 1997). Most of the histone H2A variants exhibit a unique property in addition to the N-terminal tail domain, they also posses an unstructured C-terminal tail. To date four variants of histone H2A have been discovered. These include, H2AZ, H2A.X, macroH2A and H2A.Bbd. The highest differences in the primary structure of these H2A variants are observed in their C-terminal portion. Each of these variants could be efficiently incorporated in the nucleosome in vitro and in vivo. The presence of these variants alter the structural and functional properties of the nucleosome distinctly. 

Chopped core particle means nucleosome core particle with the N-terminal tails of core histones removed by tryptic digestion. 

Role of N-terminal tails of nucleosome core histones to the accessibility of small ligands... 

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