K12-biotinylated histone H4 marks heterochromatin in human lymphoblastoma cells

Covalent modifications of histones play crucial roles in chromatin structure and genomic stability. Recently, we reported a novel modification of histones: biotinylation of lysine residues. Here we provide evidence that K12-biotinylated histone H4 (K12Bio H4) maps specifically to both heterochromatin (alpha satellite repeats in pericentromeric regions) and transcriptionally repressed chromatin (γ-G globin and interleukin-2) in human lymphoblastoma cells. The abundance of K12Bio H4 in these regions was similar to that of K9-dimethylated histone H3, a known marker for heterochromatin. Likewise, K8-biotinylated histone H4 (K8Bio H4) mapped to heterochromatin, but the relative enrichment was smaller compared with K12Bio H4. Stimulation of interleukin-2 transcriptional activity with phorbol-12-myristate-13-acetate and phytohemagglutinin caused a rapid depletion of K12Bio H4 in the gene promoter. These data are consistent with a novel role for biotin in chromatin structure and transcriptional activity of genes.