PHILADELPHIA On average, one hundred billion cells in the human body divide over the course of a day. Most of the time the body gets it right but sometimes, problems in cell replication can lead to abnormalities in chromosomes resulting in many types of disorders, from cancer to Down Syndrome.
Now, researchers at the University of Pennsylvania's School of Medicine have defined the structure of a key molecule that plays a central role in how DNA is duplicated and then moved correctly and equally into two daughter cells to produce two exact copies of the mother cell. Without this molecule, entire chromosomes could be lost during cell division.
Ben Black, PhD, assistant professor of Biochemistry and Biophysics, and Nikolina Sekulic, PhD, a postdoctoral fellow in the Black lab, report in the September 16 issue of Nature the structure of the CENP-A molecule, which defines a part of the chromosome called the centromere. This is a constricted area to which specialized molecules called spindle fibers attach that help pull daughter cells apart during cell division.
"Our work gives us the first high-resolution view of the molecules that control genetic inheritance at cell division," says Black. "This is a big step forward in a puzzle that biologists have been chipping away at for over 150 years."
Investigators have known for the last 15 years that part of cell division is controlled by epigenetic processes, the series of actions that affect the protein spools around which DNA is tightly bound, rather than encoded in the DNA sequence itself. Those spools are built of histone proteins, and chemical changes to these spool proteins can either loosen or tighten their interaction with DNA. Epigenetics alter the readout of the genetic code, in some cases ramping a gene's expression up or down. In the case of the centromere, it marks the site where spindle fibers attach independently of the underlying DNA sequence. CENP-A has bee
|Contact: Karen Kreeger|
University of Pennsylvania School of Medicine