Z* DNA, the left-handed helical form of poly[d(G-C)] in MgCl2-ethanol, is biologically active.

Sande, J.H. van de; Jovin, Thomas M.

doi:10.1002/j.1460-2075.1982.tb01133.x

Cited by 164 publications

(104 citation statements)

References 40 publications

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“…The difference in the spectroscopic effect induced by Co2+ and Ni2+ compared to the effect of Mg2+ on the 1467 cnm1 band seems to be well correlated with the efficiency of the metal ions to induce the B to Z transition in solution (1,16,18,32) and allows us to propose an explanation for the particular role of the nucleophile site in the mechanism of this transition. In conditions in which the B conformation in solution is mainly observed, the thermal agitation through the DNA respiration can modify locally the dG conformation into a syn geometry without breaking the Watson-Crick base pairing (2,7,33).…”

Section: Discussionmentioning

confidence: 77%

Interaction of Z form poly(dG-dC). poly(dG-dC) with divalent metal ions: localization of the binding sites by I.R. spectroscopy

et al. 1984

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Interacdon of Z form poly (dG-dC ABSTRACTThe secondary structures of poly(dG-dC).poly(dG-dC) in the presence of alcaline, alcaline earth and first row transition metal ions (Na+, Mg2+, Co2+, Ni2+) are investigated by infrared spectroscopy. The conformational transitions are studied as a function of the hydration of the polynucleotide and counter-ion nature and content. The use of selectively deuterated poly(dG-dC).poly(dG-dC) on the 8-carbon of guanines allows to show that a direct interaction occurs between the N7 site of guanines and the transition metal ions Co2+ and Ni2+. In the case of Mg +, for high ion/nucleotide ratios, the interaction occurs essentially at the level of the phosphate groups. This interaction leads to a modification of the left-handed conformation. Based on the IR spectroscopy results, an explanation is proposed for the different efficiencies of these various ions to induce the B -* Z transition.

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Section: Discussionmentioning

confidence: 77%

Interaction of Z form poly(dG-dC). poly(dG-dC) with divalent metal ions: localization of the binding sites by I.R. spectroscopy

et al. 1984

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“…Direct measures of ligand binding will be essential to resolve this question. Some ligands [e.g., ethidium bromide (34,35)] bind more tightly to B-DNA than to Z-DNA while others (e.g., mithramycin) bind with equal efficiency to both conformations (35). Ligands capable of covalent modification of DNA also differ in their reactivity with the two forms of DNA.…”

Section: Discussionmentioning

confidence: 99%

Secondary structure specificity of the nuclease activity of the 1,10-phenanthroline-copper complex.

Pope¹,

Sigman²

1984

Proc. Natl. Acad. Sci. U.S.A.

109

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“…The properties of poly(m5dG-dC) at 60'C were compared with those of the left-handed, aggregated Z* form of poly(dG-dC). Poly(dGdC) in 10 mM Tris.HCl/10 mM NaCl (pH 7.6) will convert from the B to the Z* form upon heating in the presence of 0.3 mM MnCl2 (19). The Z* form shows absorbance and CD spectra characteristic of the Z form DNA, but is extensively aggregated as indicated by its sedimentation under modest (12,000 x g) centrifugal fields (19).…”

Section: MM (Bp) Was Monitored As a Function Of Temperature At 300 Nmentioning

confidence: 99%

Thermodynamics of the B to Z transition in poly(m5dG-dC).

Chaires¹,

Sturtevant²

1986

Proc. Natl. Acad. Sci. U.S.A.

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Differential scanning calorimetry, temperature-dependent absorbance, and circular dichroic spectroscopy were used to study the thermodynamics of the B-Z transition in poly(m5dG-dC). In sodium phosphate buffer (pH 7.0) containing 50 mM NaCl and 1.0 mM MgCl2, the reversible B-Z transition of the polymer is centered at 38.20C and is characterized by AHw = 0.61 -0.07 kcal/(mol-base pair) (1 cal = 4.184 J), AIVH = 68 ± 7 kcal/mol, and a cooperative unit of length 110 ± 20 base pairs. A second transition centered at 53.60C is observed and represents a conformational change of poly(m5dG-dC) from the Z to an alternate left-handed form of unknown structure. This transition does not arise from aggregation to the Ze form, or from the helix-coil transition. The left-handed helix-coil transition is observed at 120.9 ± 0.3OC and is characterized by AHcw = 9.1 -1.0 kcal/(mol-base pair).These results indicate a substantial enthalpic contribution to the B-Z transition, in contrast to previous assertions that the process is entropically driven.The chemistry and biology of left-handed Z DNA are of intense current interest (1, 2). DNA sequences that are in the Z conformation (or that may be induced to adopt the Z conformation) have been identified in vivo (3-6), and a role for Z DNA in the regulation of gene expression has been proposed (1).In spite of a considerable number of fundamental studies on the B-Z transition, the thermodynamics of the process remains incompletely described. In their seminal work on the transition of poly (dG-dC) to what has proven to be the left-handed Z form, Pohl and Jovin (7) reported that the NaCl-induced transition of the polymer was independent of temperature over the range 20-50'C and inferred from their data that the van't Hoff enthalpy of the transition was near zero under their conditions. Roy and Miles (8), however, reported a thermally driven interconversion of poly(m5dG-dC) from the B to the Z form in dilute Na+/Mg2+ solutions. Temperature-dependent conformational transitions to the Z form in poly(dG-dC) and poly(m5dG-dC) under a variety of solution conditions were subsequently reported (9-14).We report here results obtained from differential scanning calorimetry (DSC) that provide a reliable estimate for the enthalpy of the B-Z transition of poly(m5dG-dC). DSC measurements provide a direct and sensitive measure of the transition enthalpy, and thus offer a significant advantage over methods based on the indirect van't Hoff analysis. Complementary absorbance and circular dichroic measurements allow us to identify the conformation of the polymer as a function of temperature. Our results provide evidence for a previously unobserved conformational transition within the left-handed DNA family. MATERIALS AND METHODSPolynucleotides. Poly(m5dG-dC) (lot 782-26 and lot NG517938) was purchased from Pharmacia P-L Biochemicals. Samples were used without further purification and were prepared by dissolving the polymer in 6 mM Na2HPO4/ 2 mM NaH2PO4/50 mM NaCl/1 mM MgCl2, pH 7.0 (henceforth referred...

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Z* DNA, the left-handed helical form of poly[d(G-C)] in MgCl2-ethanol, is biologically active.

Cited by 164 publications

References 40 publications

Interaction of Z form poly(dG-dC). poly(dG-dC) with divalent metal ions: localization of the binding sites by I.R. spectroscopy

Interaction of Z form poly(dG-dC). poly(dG-dC) with divalent metal ions: localization of the binding sites by I.R. spectroscopy

Secondary structure specificity of the nuclease activity of the 1,10-phenanthroline-copper complex.

Thermodynamics of the B to Z transition in poly(m5dG-dC).

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