Polyamine-dna interactions.Condensation of chromatin and naked dna

Ivan V. Smirnov, Stephan I. Dimitrov, Vladimir L. Makarov

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We have used flow linear dichroism (LD) and light scattering at 90° to study the condensation of both DNA and calf thymus chromatin by poly amines, such as spermine, spermidine and its analogs designated by formula NH3+(CH2)iNH2+(CH2JiNH3+, where i=2,3 and j=2,3, putrescine, cadaverine and MgCl2.It has been found that the different polyamines affect DNA and chromatin in a similar way. The level of compaction of the chromatin fibers induced by spermine, spermidine and the triamines NH3+(CH2)3NH2+(CH2)3NH3+ and NH3+(CH2)3NH2+(CH2)2NH3+ and MgCl2 is found to be identical. The triamine NH3+(CH2)3NH2+(CH2)2NH3+ and the diamines studied condense neither chromatin nor DNA This drastic difference in the action of the triamines indicates that not only the charge, but also the structure of the polycations might play essential roles in their interactions with DNA and chromatin.It is shown that a mixture of mono- and multivalent cations affect DNA and chromatin condensation competitively, but not synergistically, as claimed in a recent report by Sen and Crothers (Biochemistry 25, 1495-1503,1986).We have also estimated the extent of negative charge neutralization produced by some of the polyamines on their binding to chromatin fibers. The stoichiometry of polyamine binding at which condensation of chromatin is completed is found to be two polyamine molecules per DNA turn. The extent of neutralization of the DNA phosphates by the histones in these compact fibers is estimated to be about 55%.The model of polyamine interaction with chromatin is discussed.

Original languageEnglish
Pages (from-to)1149-1161
Number of pages13
JournalJournal of Biomolecular Structure and Dynamics
Issue number5
Publication statusPublished - Apr 1988

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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