Effects of copper and nickel on protamine like and on DNA oxidative damage in Mytilus galloprovincialis

In sperm cells, DNA is complexed with sperm nuclear basic proteins (SNBPs) to form chromatin. Although SNBPs protect DNA from a variety of potentially dangerous reactive species, such as hydroxyl radicals (•OH), chromatin packaging doesn’t protect DNA from metal ion-dependent damage in the presence of hydroxyl radicals. We report the effects induced by Cu2+ and Ni2+ ions on DNA and Mytilus galloprovincialis’ protamine-like II and III. Protamine-like III acquires proteinase k digestion resistance in the presence of copper and not in the presence of nickel; PLII, in contrast with PLIII, is sensitive to proteinase k digestion in presence of both metals. Further, copper promotes hydrogen peroxide damage of DNA also in the presence of PL-types while nickel promoting PL-types aggregation enhances DNA compactness and protection. Nickel in fact, in contrast to copper, increases PLII and PLIII DNA binding affinity. All these effects can lead an anomalous chromatin packaging and, therefore, a reduction of Mytilus galloprovincialis’ reproductive fitness and of other organisms exposed to the same toxicants.