Most cancer treatments are blunt. In an attempt to eradicate tumors, oncologists often turn to radiation or chemotherapy, which can damage healthy tissue along with the cancerous growths. New research from C. David Allis' laboratory at Rockefeller University may bring scientists closer to designing cancer therapeutics that can target tumors with pinpoint accuracy.
Their findings, published last week in Science Express, follow a recent series of discoveries by several international genome sequencing consortiums that directly links a mutated histone protein to a rare brain stem cancer in children called DIPG. Collectively, these studies represented the first time scientists had linked a histone mutation to a disease, and piqued the interest of Peter Lewis, a research associate in Allis' Laboratory of Chromatin Biology and Epigenetics, who spearheaded these new studies.
Together with DNA, histones comprise the gene packaging material called chromatin. The mutation occurs on histone H3, and involves the remarkably specific substitution of one amino acid, lysine, for another, methionine, at a key position on the histone's tail, "silencing" the associated gene. Normally, gene silencing arises when an enzyme called a methyltransferase, containing a structural region called the SET domain, attaches a methyl chemical group to the lysine at position 27 in the H3 tail. This highly specific chemical reaction, called methylation, is disrupted by the replacement of the lysine with methionine, which could result in gene mis-regulation.
Lewis and his colleagues looked at human DIPG tumors that contained the lysine-to-methionine substitution and determined that mutated histone H3 comprised anywhere from 3.6 percent to 17.6 percent of total H3 in DIPG samples. They also found a global reduction in the levels of methylation of normal H3 histones when small amounts of the mutant H3 were added to normal human cells.
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|Contact: Joseph Bonner|