Nucleohistones

In this connection, it must also be borne in mind that the deoxyribonucleic acids subjected to analysis have probably not been homogeneous. Deoxyribonucleic acids have been fractionated by making use of their different solubilities in normal saline,186 by extracting thymus nucleo-his-tone with sodium chloride solutions of increasing concentration,187 by ion-exchange,187 and also by adsorption of the polynucleotide onto histone immobilized on a kieselguhr support.123 It is possible, however, that these are artefacts, since it has been shown that deoxyribonucleic acid fractions extracted from calf-thymus nucleohistone may or may not vary in composition according to the previous treatment of the material.188... 

Datta, A.K., S.L. North, K.S. Kasprzak. 1994. Effect of nickel (II) and tetraglycine on hydroxylation of the guanine moiety in 2 -deoxyguanosine, DNA, and nucleohistone by hydrogen peroxide. Sci. Total Environ. 148 207-216. 

It is interesting to note that nucleohistone lacking amino termini does not aggregate as readily in the presence of MgCl as do untreated particles (Whitlock and Stein, 1978). It might be hypothesized from this result that, although the amino termini are not necessary for the maintenance of nucleosome structure, they are involved in vivo in in-temucleosomal interactions. 

Chaires JB, Herrera JE, Waring MJ (1990) Preferential binding of daunomycin to 5-ATCG and 5-ATGC sequences revealed footprinting, titration experiment. Biochemistry 29 6145-6153 Chakrabarti S, Mahmood A, Kassis AI, Bump EA, Jones AG, Makrigiorgos GM (1996) Generation of hydroxyl radicals by nucleohistone-bound metal-adriamycin complexes. Free Radic Res... 

Dds is the inter-duplex separation for complexes of MX-DNA. Dds is calculated from the apparent transfer distance, Da(l ), which is increased by transfer between duplexes and the actual transfer distance along one duplex, Di(l ), via Eq. 10, assuming Di(l ) is the same for both MX-DNA and MX-DNA solid complexes at similar hydration states. All are calculated assuming n= 6 except MX-nucleohistone for which n was assumed to be 4.5... 

A study has been made of the DNA secondary structure induced by the various nucleohistone complexes 342). The interaction of calf thymus DNA with the anticancer drug Cisplatin in water and heavy water has been studied. The carbonyl bands at 1710 and 1686 cm-1 of the control DNA disappear and shift to lower frequencies in the spectra of the products of the reaction. The drug induces a reorganization of the water molecules and the DNA structure is modified 340). 

Salt bridges between positively charged basic amino acid side chains of histones and the negatively charged DNA phosphates play a major role in stabilizing the DNA-histone complex. Indeed, treatment of chromatin with concentrated NaCl (1-2 m), which is known to disrupt electrostatic bonds, causes a complete dissociation of DNA and histone in the nucleohistone complex. 

Davies MJ, Gilbert BC, Norman ROC (1984) Electron spin resonance, part 67. Oxidation of aliphatic sulphides and sulphoxides by the sulphate radical anion (S04 ) and of aliphatic radicals by the peroxydisulphate anion S Os2 ). J Chem Soc Perkin Trans 2 503-509 Dizdaroglu M, Gajewski E, Reddy P, Margolis SA (1989) Structure of a hydroxyl radical induced DNA-protein cross-link involving thymine and tyrosine in nucleohistone. Biochemistry 28 3625-3628... 

It will be shown below that alkyl radicals add predominantly at the C(6)-positions of the pyrimidines and, when products as shown above are found after OH-attack in very complex systems such as nucleohistones (e.g., Gajewski et al. 1988 Dizdaroglu and Gajewski 1989 Dizdaroglu et al. 1989 Gajewski and Dizd-aroglu 1990) or Thy dimers in polydeoxythymidylic acid (Karam et al. 1986), it cannot be fully excluded that they are formed via the trivial two-radical recombination mechanism. 

Gajewski E, Dizdaroglu M (1990) Flydroxyl radical induced cross-linking of cytosine and tyrosine in nucleohistone. Biochemistry 29 977-980... 

Gajewski E, Fuciarelli AF, Dizdaroglu M (1988) Structure of hydroxyl radical-induced DNA-protein crosslinks in calf thymus nucleohistone in vitro. Int J Radiat Biol 54 445-459 Gajewski E, Rao G, Nackerdien Z, Dizdaroglu M (1990) Modification of DNA bases in mammalian chromatin by radiation-generated free radicals. Biochemistry 29 7876-7882 Garner A, Scholes G (1985) Mechanism of the photohydration of pyrimidines a flash photolysis study. Photochem Photobiol 41 259-265... 

Many new applications of gel electrophoresis will undoubtedly be devised, and the method should prove itself as generally versatile and advantageous in the study of viruses, nucleohistones, nucleo-... 

Brutlag D, Schlehuber C, Bonner J. 1969. Properties of formaldehyde-treated nucleohistone. Biochemistry 8 3214-3218. 

Schmidt, G., The effect of enzymes on protein with prosthetic groups. I. The effect of nucleophosphatase on thymus nucleohistone. Enzymologia 1, 135-141 (1936). 

Binding between DNA and poly-L-lysine at pH 7 was monitored at various molar ratios of the complex components by measurement of ORD changes in the range 220 to 360 nm. These changes could be compared with those occurring in DNA-protein complexes (see below, nucleohistones). Possible interpretations included tilting of the bases... 

CD spectra (200—350 nm) of calf thymus chromatin were compared with those of pure DNA in solution. Some of the differences observed (above approximately 250 nm) were attributed to conformational changes in the bound DNA, in which a large tilting of the bases may occur [(373) and refs, cited therein]. Previously, similar conclusions had been reached on the basis of ORD measurements on native nucleohistone and on nucleohistone dissociated either fully or partially into DNA and histone [(374) see also (375—379)]. CD studies on the state of DNA in native and partially deproteinized gander erythrocyte chromatin and of complexes of ethidium bromide with these systems were reported (380). 

Each prokaryotic chromosome consists of a supercoiled circular DNA molecule com-plexed to a protein core. Each eukaryotic chromosome consists of a single linear DNA molecule that is complexed with histones to form nucleohistone. 

Each eukaryotic chromosome is composed of nucleohistone, a complex formed by winding a single DNA molecule around a histone octomer to form a nucleosome. The DNA of mitochondria and chloroplasts is similar to the chromosomes found in prokaryotes. 

Fig. 12.6. Infrared absorption spectrum of partial nucleoprotein which was obtained by exposing calf thymus nucleohistone to 1.2M NaCI.

Bradbury et al. (1967) have studied partial nucleoproteins produced by removal of histone fractions from nucleohistone. Figure 12.6 shows a polarized infrared spectrum of one of the nucleoproteins oriented by shearing. The spectrum is that of a film deuterated by D2O vapor. The bands of the in-plane vibrations of cytosine and guanine moieties are highly polarized when the electric vector is placed perpendicular to the fiber axis. The 1452 cm absorption is that of the amide IF band (Miyazawa et al., 1956 Miyazawa, 1962) for the readily deuterated fraction of the partial nucleoprotein. As seen in Fig. 12.6, the 1452 cm band is polarized considerably in the direction parallel to the fiber axis, giving evidence that the extended polypeptide chain is situated so that its axis lies between the angle of the groove in the DNA double helix and the axis of the DNA helices (Bradbury et al., 1967). 

In nucleohistone, there is a component which requires more than three weeks for complete deuteration to take place in D2O vapor of 94 % r.h. (Bradbury et al, 19626 Kyogoku, 1963), although nucleoprotamine deuterates very fast, the protein and DNA components becoming completely deuterated within a few minutes of exposure of the film in D2O vapor of 94% r.h. (Bradbury et al., 1962a Kyogoku, 1963). These results are explained by considering that nucleoprotamine does not contain any a-helical part but nucleohistone does contain the a-helix (Tsuboi, 1969). 

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