Folding of DNA into chromatin is mediated by binding to histones such as H4; association of DNA with histones is regulated by covalent histone modifications,. acetylation, methylation, sought to identifyamino-acid residues that are biotinylated in histone H4,and to determine whether acetylation and methylation of histones affect biotinylation. Synthetic peptides spanning fragments of human histone H4 were biotinylated enzymatically using biotinidase. Peptide-bound biotin was probed with strept-avidin–peroxidase
