KANSAS CITY, MOTwo opposing teams battle it out to regulate gene expression on the DNA playing field. One, the activators, keeps DNA open to enzymes that transcribe DNA into RNA. Their repressor opponents antagonize that effort by twisting DNA into an inaccessible coil around histone proteins, an amalgam called chromatin, effectively blocking access to DNA by enzymes that elongate an RNA strand.
Both teams maneuver by chemically modifying histonesthe activators by decorating histones with acetyl groupslet's call them green flagscausing them to loosen their grip on DNA. The repressors retaliate by marking histones with red flags, often methyl groups, which call in de-acetylase enzymes to clip off the green flags, restore the chromatin barrier and end that round of gene expression. Disturbing this biochemical balance lies at the heart of many diseases, particularly cancer.
Recently, the lab of Jerry Workman, Ph.D., investigator at the Stowers Institute for Medical Research, reported in the journal Nature that a reserve of "pre-acetylated" histones sits on the chromatin sidelines ready to sub for histones whose green flags get clipped by repressors, a tactic aiding the activators called "histone exchange". In a companion study published in the Aug. 26, 2012 Advance Online Publication of Nature Structural & Molecular Biology the Workman lab now shows that a repressor called Set2 in yeast recruits a protein assistant to block the histone exchange. That study reveals a heretofore unknown mechanism to keep gene activation under control and ensure that erroneous transcription does not occur.
"Accurate gene expression is critical for normal cell function, and when this control is lost cells grow abnormally," says Workman. "These two studies identify mechanisms used by cells to regulate gene expression, which is important for our understanding of what goes wrong in diseases marked by unregulated cell growth, like ca
|Contact: Gina Kirchweger|
Stowers Institute for Medical Research