title: A protein fraction stably linked to DNA in plant chromatin.
abstract: DNA from the chromatin of roots and shoots of maize seedlings was isolated and extensively deproteinized by repeated high-salt extractions, by subsequent deproteinizations eliminating noncovalently associated proteins and by CsC1 density gradient centrifugation. Nevertheless, a protein component resisting all extraction procedures was found firmly associated to plant nuclear DNA. This component was responsible for the (125)I uptake when a DNA preparation had been labeled by the chloramine-T method.A residual oligodeoxynucleotide-oligopeptide complex was obtained after extensive digestions of the initial DNA-protein complex with proteases and nucleases. The stability of this complex to different chemical treatments suggested a phosphoester type of a linkage. The hydrolysis of this complex by phosphodiesterases indicated that the protein component was linked to plant chromosomal DNA through a phosphodiester bond formed by a hydroxyaminoacid and a 5'-end DNA phosphate. Two-dimensional tryptic peptide mapping of the proteins isolated from the two maize chromatins revealed a high degree of similarity to the corresponding proteins of animal origin. Its conservative structure suggests an important role for this protein component in the functioning of the eukaryotic genome.
authors.affiliation: Institute of Molecular Biology, Bulgarian Academy of Sciences, 1113, Sofia, Bulgaria.
authors.forename: Z
authors.initials: Z
authors.lastname: Avramova
authors.forename: M
authors.initials: M
authors.lastname: Ivanchenko
authors.forename: R
authors.initials: R
authors.lastname: Tsanev