LA JOLLA, CA----For humans to grow and to replace and heal damaged tissues, the body's cells must continually reproduce, a process known as "cell division," by which one cell becomes two, two become four, and so on. A key question of biomedical research is how chromosomes, which are duplicated during cell division so that each daughter cell receives an exact copy of a person's genome, are arranged during this process.
Now, scientists at the Salk Institute have discovered a new characteristic of human cell division that may help explain how our DNA is organized in the nucleus as cells reproduce. They found that telomeres, molecular caps that protect the ends of the chromosomes, move to the outer edge of the cell's nucleus after they have been duplicated.
While the implications of this spatial reorganization of telomeres are not yet clear, the findings may shed light on how our genes are regulated and how gene expression programs are altered during cell division, an important step in understanding aging and diseases that stem from genetic mutations, such as cancer.
"What we discovered is that telomeres not only protect our chromosomes, they also help organize our genetic material in the nucleus," says Jan Karlseder, a professor in Salk's Molecular and Cell Biology Laboratory and the Donald and Darlene Shiley Chair. "This is important, because the three-dimensional position of DNA in the nucleus influences gene expression profiles and how the genome morphs over time."
Telomeres, a combination of proteins and DNA, are crucial in DNA replication, tumor suppression and aging. Every time a primary human cell divides, its telomeres get shorter, until critically short telomeres lead cells to self-destruct. Much of Karlseder's research has focused on understanding telomere dynamics in order to develop ways to influence the aging process, and as a result, restrict cancer cell growth.
In addition to exploring the involvement of
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