HistoneH3 (21-44)-GK-biotin is a peptide fragment of histoneH3 that corresponds to amino acid residues 22-45 of the human histoneH3.1 and 3.2 sequences and is biotinylated via a C-terminal GK linker. HistoneH3 (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. HistoneH3 (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.
HistoneH3 (21-44)-GK-biotin is a peptide fragment of histoneH3 that corresponds to amino acid residues 22-45 of the human histoneH3.3 sequence and is biotinylated via a C-terminal GK linker. Unlike histoneH3.1 and H3.2, the histoneH3.3 variant contains a serine residue at position 31 that is phosphorylated during late prometaphase and metaphase of mitosis. HistoneH3 (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 histoneH3phosphorylation and may alter epigenetic regulation of cell proliferation. On a related note, fostriecin was first identified as an antitumor antibiotic.