Research Offers Insight Into Body's Own Health-Maintenance Mechanism

Researchers have verified the importance of a “bookmarking” phenomenon that might explain how cells are able to respond quickly to stress following cell division -- an important protective mechanism against cell death.

The study, co-authored by Yiling Hong, PhD, and Chris Mayhew, PhD, both of UC's Department of Cell Biology, Neurobiology and Anatomy, looked at the stress-response gene hsp70i, one of a class of genes known to help a cell survive a stressing event.

The researchers sought to determine whether the gene’s regulation during cell division was significant in the cell’s rapid response to common stresses placed on cells, including heat stress.

They found that, unlike the vast majority of other genes, hsp70i is more accessible just prior to and immediately following cell division (mitosis). This is due to a process known as bookmarking, which allows the gene to “turn itself on” faster in reaction to various types of stress.

The study, led by Kevin Sarge, PhD, of the University of Kentucky, was funded by the National Institutes of Health (NIH) and appears in the Jan. 21, 2005, issue of Science. Drs. Mayhew and Hong were at the University of Kentucky for most of the project.

When cells divide during mitosis, chromosomes are packed tightly together immediately before and after cell division. For some genes, however, DNA regions that dictate whether a gene can be turned on remain more accessible (less tightly packed) and act like bookmarks in the way they jut out of the tightly packed chromosomes.

It is too early to predict implications of this research, Dr. Mayhew says, but “it’s a significant finding.”

“This work provides insight into how our cells efficiently protect themselves from stress,” he says, “which is of course a general requirement for the maintenance of human health.”

Bookmarking and efficiently turning on hsp genes is of major importance, Dr. Hong says.

“If bookmarking is lost, cells die at a faster rate because they can’t respond to stress as quickly as they should,” she says.