Histone H3 (21-44)-GK-biotin is a peptide fragment of histone H3 that corresponds to amino acid residues 22-45 of the human histone H3.1 and 3.2 sequences and is biotinylated via a C-terminal GK linker. Histone H3 (21-44) contains a lysine residue at position 23 that is subject to acetylation, an arginine at position 26 subject to methylation, and a serine at position 28 subject to phosphorylation, as well as lysine residues at positions 27 and 36 that are subject to methylation and acetylation. Histone H3 (21-44)-GK-biotin has been used as a substrate for the primate-specific histone methyltransferase PR domain-containing protein 7 (PRDM7) to determine substrate specificity.
Histone H3 (21-44)-GK-biotin is a peptide fragment of histone H3 that corresponds to amino acid residues 22-45 of the human histone H3.3 sequence and is biotinylated via a C-terminal GK linker. Unlike histone H3.1 and H3.2, the histone H3.3 variant contains a serine residue at position 31 that is phosphorylated during late prometaphase and metaphase of mitosis. Histone H3 (21-44) also contains lysine residues at positions 23, 27, and 36 that are subject to methylation and acetylation, all of which have a role in the regulation of gene expression, and a serine residue at position 28 that is subject to phosphorylation during mitosis.
Fostriecin (free base) is an inhibitor of the serine/threonine protein phosphatases 2A (PP2A) and 4 (PP4) (IC50s = 3.2 and 3 nM, respectively). It less effectively inhibits topoisomerase II and PP1 (IC50s = 40 and 131 μM, respectively) and does not inhibit PP2B. Through its effects on protein phosphatases, fostriecin increases the level of histone H3 phosphorylation and may alter epigenetic regulation of cell proliferation. On a related note, fostriecin was first identified as an antitumor antibiotic.