CHAMPAIGN, Ill. -- A new, non-invasive method for tagging chromosomes is making genetic activity in living cells easier to see, and likely will lead to insights into chromosome movements, folding and unfolding during natural events such as cell division, DNA replication and transcription.
Since the method was announced by University of Illinois researchers in December 1996, it has been applied by several laboratories in live cells taken from bacteria, yeast and mammals, as well as from Drosophila (fruit flies) and C. elegans (worms).
In an upcoming issue of Trends in Cell Biology, the use of the technique will be detailed by Andrew S. Belmont, a professor of cell and structural biology at the U. of I., and Aaron F. Straight, a physiologist in the School of Medicine at the University of California at San Francisco.
"This method is opening a clearer window into the working mechanics in cells," Belmont said. "It gives us a way to look at the dynamics that hasn't been possible before. Down the road, we would like to learn what happens to the structure of a chromosome when a gene is turned on or off."
The method uses a specific protein-DNA interaction in which a protein binds to a specific target in DNA without altering chromosomal structure. The traditional DNA hybridization technique for localizing a particular chromosome region cannot be done on living cells, and it causes some damage, a problem that has seriously limited structural and mechanical research on chromosomes.
Belmont created a roughly 10,000-base pair DNA fragment containing 256 copies of the lac-operator sequence to which the lac-repressor protein binds. The interaction between the operator and repressor, found normally in bacteria, is well-described by previous work. By detecting the lac-repressor protein, the location of the DNA fragment containing the lac-operator repeats is revealed.