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New research from the Korea Institute of Science and Technology, to be published in the Journal of Biological Chemistry on Oct. 13, has found that the proteasome, an essential protein complex that breaks down proteins in cells, has another unexpected function: directly regulating the packing of DNA in the nucleus.
The proteasome breaks down proteins that the cell has tagged for degradation in a process called proteolysis. Dysfunction in the proteasome has been observed in diseases of many physiological systems, from the immune, nervous and cardiovascular systems to the whole organism's aging processes. Increasing research suggests that, like a Swiss army knife with hidden tools, the proteasome is able to perform additional functions that don't involve proteolysis.
DNA - Nucleus - Complexes - Protein - Nucleus
DNA is organized in the nucleus in complexes with protein in the nucleus in a form called chromatin. Broadly speaking, loosely packed chromatin, or euchromatin, allows DNA to be transcribed and genes to be expressed, whereas tightly packed heterochromatin prevents gene expression.
In experiments using yeast cells, Hogyu David Seo, a graduate student in Daeyoup Lee's lab, found that the proteasome could induce heterochromatin to form in some parts of the genome but stop it from spreading to other regions. Surprisingly, the mutations in the proteasome that revealed the proteasome's effects on chromatin had no effect on proteolysis, meaning that the proteasome affects heterochromatin through an activity other than proteolysis....
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