Related Experiment Videos
DNA-protein crosslinking by heavy metals in Novikoff hepatoma
Abstract:
Crosslinking of proteins to DNA was studied in live intact Novikoff ascites hepatoma cells exposed in vitro to salts of chromium VI, III, and II, nickel II, cadmium II, and to CoCl2, As2O3, and AlK(SO4)2. DNA-protein complexes were separated by high-speed centrifugation of cells solubilized in buffered 4% sodium dodecyl sulfate and assayed by polyacrylamide gel electrophoresis. Hexavalent chromium compounds formed DNA-protein complexes very efficiently. The trivalent, poorly soluble, cupric chromite was nearly as efficient crosslinker as hexavalent Cr, perhaps because phagocytosis facilitated its entry into the cells. The more basic divalent form produced hardly any crosslinks. Most of the crosslinked proteins were common to all of the chromium salts employed. Nickel salts formed DNA-protein crosslinks less efficiently. Most proteins crosslinked by this metal had a high molecular weight ranging from 94,000 to 200,000. There was little qualitative difference between the crosslinked protein patterns for several various nickel (II) salts. Similar results were obtained for cells incubated with cadmium salts. Most of the proteins crosslinked by cadmium had high molecular weights and were similar to those crosslinked by nickel (II). Relatively weak, but significant, crosslinking was also observed when the Novikoff hepatoma cells were exposed to CoCl2, As2O3, or AlK(SO4)2.
Insights
Chromium VI compounds efficiently crosslink proteins to DNA in hepatoma cells. Other metals like nickel and cadmium also induced DNA-protein crosslinking, affecting high molecular weight proteins.
Area of Science:
- Biochemistry
- Molecular Biology
- Toxicology
Background:
- Understanding how metal ions interact with cellular components is crucial for toxicology and cancer research.
- DNA-protein crosslinking can disrupt cellular processes and lead to genotoxicity.
Purpose of the Study:
- To investigate the ability of various metal salts to induce DNA-protein crosslinking in Novikoff ascites hepatoma cells.
- To characterize the proteins involved in metal-induced DNA-protein crosslinking.
Main Methods:
- Exposure of live Novikoff ascites hepatoma cells to different metal salts in vitro.
- Separation of DNA-protein complexes using high-speed centrifugation after cell solubilization.
- Analysis of crosslinked proteins by polyacrylamide gel electrophoresis.
Main Results:
- Hexavalent chromium (Cr VI) compounds were highly efficient in forming DNA-protein complexes.
- Trivalent chromium (Cr III) compounds, particularly cupric chromite, were also effective crosslinkers.
- Nickel (Ni II) and cadmium (Cd II) salts induced crosslinking, primarily involving high molecular weight proteins (94,000-200,000 Da).
- Cobalt (CoCl2), arsenic (As2O3), and aluminum (AlK(SO4)2) showed weaker but significant crosslinking activity.
Conclusions:
- Chromium, especially Cr VI, is a potent inducer of DNA-protein crosslinking in hepatoma cells.
- Nickel and cadmium exhibit crosslinking capabilities, targeting specific high molecular weight proteins.
- The study provides insights into the genotoxic potential of various metal ions through DNA-protein complex formation.