title: Biotin is not a natural histone modification.
abstract: In addition to its role as the cofactor of biotin-dependent carboxylases, biotin has been demonstrated to have a role in cellular processes including transcription and gene silencing. Histones have been proposed to be modified by biotin in a site-specific manner, providing a pathway by which biotin acts as a regulatory molecule for gene expression. However, there is uncertainty whether biotin attachment to histones in vitro can be extrapolated to biotin as a native histone modification. We critically examined a number of methods used to detect biotin attachment on histones, including [(3)H]-biotin uptake, Western blot analysis of histones, and mass spectrometry of affinity purified histone fragments with the objective of determining if the in vivo occurrence of histone biotinylation could be conclusively established. We found for each of these methods that, while biotin could be readily detected on native carboxylases or histones biotinylated in vitro, biotin attachment on native histones could not be detected in cell cultures from various sources. We conclude that biotin is absent in native histones to a sensitivity of at least one part per 100,000, suggesting that the regulatory impact of biotin on gene expression must be through alternate mechanisms.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada T2N 4N1. shannon.healy@tut.fi
authors.forename: Shannon
authors.initials: S
authors.lastname: Healy
authors.forename: Beatriz
authors.initials: B
authors.lastname: Perez-Cadahia
authors.forename: Dongxin
authors.initials: D
authors.lastname: Jia
authors.forename: Megan K
authors.initials: MK
authors.lastname: McDonald
authors.forename: James R
authors.initials: JR
authors.lastname: Davie
authors.forename: Roy A
authors.initials: RA
authors.lastname: Gravel
mesh_terms: D000595:Amino Acid Sequence; D000906:Antibodies / Q000378:metabolism; D001360:Avidin / Q000737:chemistry / Q000378:metabolism; D001710:Biotin / Q000737:chemistry / Q000378:metabolism*; D019921:Biotinylation; D015153:Blotting, Western; D003470:Culture Media / Q000737:chemistry; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006657:Histones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D011485:Protein Binding; D046188:Protein Modification, Translational; D012685:Sepharose / Q000737:chemistry / Q000378:metabolism; D014316:Tritium
chemical_list: D000906:Antibodies; D003470:Culture Media; D006657:Histones; C093483:neutravidin; D014316:Tritium; D001360:Avidin; D001710:Biotin; D012685:Sepharose