Partitioning of zinc and copper within subnuclear nucleoprotein particles

Abstract

Nuclei from frozen calf thymus suspended in buffer were analyzed for metal content prior to and after repeated washing. After three such extractions about 0.1 micrograms Zn/mg DNA and 0.025 micrograms Cu/mg DNA remained tightly associated with chromatin. This level of metal was essentially unchanged with subsequent washings. Digestion of extracted nuclei with micrococcal nuclease yielded soluble nucleoprotein containing zinc and copper. Metal enriched regions of chromatin appeared to be preferentially solubilized by digestion, and the solubilized metal was only partially dializable either with or without EDTA. Metal profiles generated from gel (A-5m) chromatography analysis of chelated and non-chelated solubilized chromatin were distinctive in that copper was undetectable (by flame AA) while zinc was associated only with low molecular weight products when EDTA was used. In contrast, both metals were detected with higher molecular weight oligonucleosomes in the absence of chelating agents. Additionally, the two metals localized within nucleoprotein peaks and these metal-containing regions were only resolved by gel chromatography when EDTA was omitted throughout the procedure. A discrete Cu-rich species in a region of the profile suggests a subset of Cu-rich nucleoprotein complexes.

Formation of 8-Oxo-7,8-dihydro-2‘-deoxyguanosine (8-Oxo-dGuo) by PAH o-Quinones: Involvement of Reactive Oxygen Species and Copper(II)/Copper(I) Redox Cycling

“…Cu(II) is protein bound and is present in higher concentrations in the nucleus than in the cytosol (53). In the nucleus, copper exists in a nuclear histone protein complex located at the base of DNA loops, where it maintains the nuclear matrix and DNA folding (54,55).…”

Efficient DNA Cleavage Induced by Copper(II) Complexes of Hydrolysis Derivatives of 2,4,6‐Tri(2‐pyridyl)‐1,3,5‐triazine in the Presence of Reducing Agents

“…[4,5] Moreover, copper is an important structural metal ion in chromatin, [6][7][8] which contains about one copper ion per kilobase. [6] For these reasons, there is an increased interest in the ability of copper ion to participate in DNA-damaging reactions in vivo.…”

“…[6] For these reasons, there is an increased interest in the ability of copper ion to participate in DNA-damaging reactions in vivo. [8,9] Kinetic, [9][10][11] inhibitor, [4,5,9] and sequence-context [12][13][14][15] studies have all suggested that DNA damage induced by copper ion in the presence of H 2 O 2 occurs site-specifically at the sites of DNA-associated copper. However, the nature of the last DNA-oxidizing species produced by the interaction of the DNA-Cu I complex with H 2 O 2 remains uncertain.…”

Involvement of DNA Conformational Change Induced by Rearrangement of Copper-coordination Geometry in Oxidative DNA Damages Caused by Copper and Dopamine

“…11) Copper exists in the cell nucleus at a relatively high concentration and closely associates with chromosomes and bases, 12,13) although its free ion form is absent in the body. 14) Thus, changes in DNA conformation could be involved in metal-mediated genotoxicity as well as oxidative damage but via different mechanism.…”