Histone H3 (10-29)-Biotin – Biotin Labeled

Histone H3 (10-29)-Biotin is derived from Histone 3 (H3) which is one of the four core histones (H2A, H2B, H3 and H4) fundamental in compacting eukaryotic DNA into the nucleosome. The nucleosome arises when 147 base pairs of DNA wrap around a H3-H4 tetramer and two H2A-H2B dimers, forming the histone octamer core. Both H4 and H3 are highly conserved and perform roles in binding to segments of DNA which enter and leave the nucleosome and in chromatin formation. Similar to the other core histone, H3 has a globular domain and a flexible N-terminal domain, ‘histone tail’ which can undergo modifications such as acetylation, methylation, phosphorylation and ubiquitination. Due to histones containing a large number of lysine and arginine residues they have a positive net charge which interacts in an electrostatic manner with the negatively charged phosphate groups in DNA. The transcriptional activation or silencing of the chromatin is controlled by ATP-dependent chromatin remodelling factors and histone modifying enzymes which target histone proteins. Both processes function to alter the positioning of the nucleosome, allowing the DNA it to be either available or inaccessible to the transcription machinery. Another modification process histones can undergo is biotinylation where the covalent attachment of a biotin molecule is catalysed by the enzyme Biotinidase. This cleaves biocytin to generate a biotinyl-thiester intermediate. The biotinyl can then be transferred onto the histone lysine ɛ-amino group which is covalently attached to Histone 3. Overall the biotinylation sites identified in histone 3 are: K4, K9 and K18. The presence of biotinylated histones have been detected in human cells such as lymphocytes and lymphomas.