title: Interactions of H1 and H5 histones with polynucleotides of B- and Z-DNA conformations.
abstract: Interactions of chicken H1 and H5 histones with poly(dA-dT), poly(dG-dC), and the Z-DNA structure brominated poly(dG-dC) were measured by a nitrocellulose filter binding assay and circular dichroism. At low protein:DNA ratios, both H1 and H5 bound more Z-DNA than B-DNA, and binding of Z-DNA was less sensitive to interference by an increase in ionic strength (to 600 mM NaCl). H5 histone bound a higher percentage of all three polynucleotides than did H1 and caused more profound CD spectral changes as well. For spectral studies, histones and DNA were mixed in 2.0 M NaCl and dialyzed stepwise to low ionic strength. Prepared in this way or by direct mixing in 150 mM NaCl, complexes made with right-handed poly(dG-dC) showed a deeply negative psi spectrum (deeper with H5 than with H1). Complexes of histone and Br-poly(dG-dC) showed a reduction in the characteristic Z-DNA spectral features, with H5 again having a greater effect. Complexes of poly(dA-dT) and H5, prepared by mixing them at a protein:DNA ratio of 0.5, displayed a distinctive spectrum that was not achieved with H1 even at higher protein:DNA ratios. It included a new negative band at 287 nm and a large positive band at 255 nm, giving the appearance of an inverted spectrum relative to spectra of various forms of B-DNA. These findings may reflect an ability of the different lysine-rich histones to cause varying conformational changes in the condensation of chromatin in DNA regions of highly biased base sequence.
mesh_terms: D000818:Animals; D002417:Cattle; D002645:Chickens; D002942:Circular Dichroism; D003101:Collodion; D005374:Filtration; D006657:Histones / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D009994:Osmolar Concentration; D011067:Poly dA-dT / Q000378:metabolism*; D011089:Polydeoxyribonucleotides / Q000378:metabolism*
chemical_list: D006657:Histones; D011089:Polydeoxyribonucleotides; D011067:Poly dA-dT; C019530:poly(dC-dG); D003101:Collodion; C043078:poly(dG-Br(5)dC).poly(dG-Br(5)dC)