Other scientists had already identified positively charged atoms called cations as neutralizing factors. They found that dinoflagellate chromosomes explode upon the removal of calcium and magnesium cations.
Levi-Setti has produced the first images of the distribution of these cations in dinoflagellate chromosomes. These images verify that cations, mainly of calcium and magnesium, neutralize DNA's enormous negative charge, and further suggest a critical role in folding the protein as well.
The finding raises questions about the evolution of chromosomes, Rizzo said. "Did dinoflagellates once have histones and then lost them? Or did dinoflagellates never have histones and just 'figured out' a different way to fold large amounts of DNA into chromosomes?" Rizzo asked.
The images were produced using a high-resolution scanning ion microprobe, an instrument that Levi-Setti developed in the 1980s jointly with Hughes Research Laboratories in Malibu, Calif. For the last 15 years, Levi-Setti has collaborated with associates of pioneering chromosome researcher Janet Rowley, the Blum-Riese Distinguished Service Professor in Medicine, Molecular Genetics & Cell Biology and Human Genetics at the University of Chicago.
In 2001, the collaboration demonstrated that cations play an important role in compacting mammalian DNA and helping chromosomes maintain their structure. "Chromosomes would fall apart when calcium and magnesium were removed," Levi-Setti said.
Wondering if there could be a fundamental evolutionary process at work, Levi-Setti extended his research to the fruit fly. Like mammals, fruit flies belong to the pantheon of eukaryotes. In contrast to prokaryotes like bacteria, eukaryotes pack their genetic material in a cellular nucleus. Prokaryotes lack a nucleus.
"Cations play a very important role in the folding and charge neutralization of DNA in all
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