This extensive chromosomal "remodeling" is accomplished by moving DNA packaging structures called nucleosomes to different spots in the genome. Once a nucleosome is moved from a site, the appropriate gene then can be expressed much more efficiently.
The new findings appear online in the journal Nature Genetics. The study will be published in the August print edition.
The UNC researchers also discovered that when a gene needs to be turned off, the cell recruits the nucleosomes back to a particular location in the genome, thus helping to ensure that expression of the gene is stopped.
Nucleosomes are complexes of proteins that were thought to simply bind to genomic DNA and condense it into structures called chromatin that can fit inside a cell's nucleus. It was historically assumed that nucleosomes were uniformly distributed throughout the genome and that this distribution was unchanging. The new study overturns this assumption, the UNC researchers said.
"Except for at a few genes, it was traditionally thought that there was a monotonic organization of chromatin that did not vary throughout the genome," said senior author Dr. Jason Lieb, assistant professor of biology in UNC's College of Arts and Sciences and a member of the Carolina Center for Genome Sciences.
"But chromatin is a dynamic thing - much more dynamic than was once thought."
The study also suggested a new role for the nucleosome as a regulator of gene expression.
"We now know that nucleosomes mark territory," said co-author Dr. Brian Strahl, assistant professor of biochemistry and biophysics in UNC's School of Medicine. "This chromosomal remodeling allows the work of gene expression to occur."
The study
'"/>
Contact: Leslie H. Lang
llang@med.unc.edu
919-843-9687
University of North Carolina School of Medicine
29-Jul-2004