Each of our cells contains a lot of DNA. So much DNA, in fact, that it has to be elaborately condensed and organized into chromosomes, which are then packed into the cell’s nucleus. If completely unraveled, the genetic material from just one of our 46 chromosomes would stretch out to 1.5 centimeters – 10,000 times the length of the packed chromosome.To condense all of this genetic material, long strands of DNA are tightly wound around proteins called histones. All this packing, however, can present a problem when our cellular machinery needs to access our DNA to read genes and produce proteins. As a result, chromosome packing is dynamic – some areas stay tightly wound while others are looser. Just how accessible a particular region is can vary, depending on the tissue type, stage of development, disease state and other factors.
Dr. Sepideh Khorasanizadeh, one of Sanford-Burnham’s newest faculty members in Lake Nona, Florida, studies the cellular signals that influence chromosome packing to turn genes on and off. While much is known about how cells receive signals from the environment and carry those signals across into the cytoplasm, what happens when they reach the nucleus remains a mystery.