CHAMPAIGN, lll. A protein that helps pack DNA into the cell nucleus has an important role in regulating gene activity, scientists report. The researchers found that the protein, histone H1, also takes part in the formation of ribosomes, the cellular workbenches on which all proteins are made.
The study appeared online May 3 in the Journal of Cell Biology.
A human cell's genetic material is so vast that it must be condensed into tightly wound structures resembling beads on a string. The DNA winds around four core histone proteins to form one of the "beads" while H1 or "linker" histones clamp the DNA into place where it enters and exits the beads. One bead and its associated DNA make up a nucleosome. There are well over a million nucleosomes in the nucleus of a cell.
There are many varieties of the H1 histone protein in animals, making the histones difficult to study. Most research into histone biology has focused on the core histones, and previous studies have found that various cellular modifications of these other histones coincide with changes in gene activity.
The new study found that when H1 histones are modified by the addition of a phosphate group, a process called phosphorylation, that modification is associated with changes in gene activity in the vicinity of the phosphorylated histone.
"Most studies of histone phosphorylation have focused on cell division, when phosphorylation is at its peak," said Craig Mizzen, a professor of cell and developmental biology at the University of Illinois and corresponding author on the study. During cell division "much less of the genome is transcribed than at other points in the cell cycle," Mizzen said. "Everything is geared toward separating the replicated genome copies equally between the new daughter cells."
Suspecting that H1 phosphorylation was important for processes besides cell division, Mizzen and his colleagues identified the exact sites in H1 t
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University of Illinois at Urbana-Champaign