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    St. Jude study yields secrets of chromosome movement

    Janet F. Partridge, PhD

    St. Jude investigators have used the lowly yeast to gain insights into how a dividing human cell ensures that an identical set of chromosomes gets passed on to each new daughter cell. Errors in this critical part of cell division can cause one daughter cell to get extra copies of some chromosomes that should have moved into the other daughter cell, or no copies of other chromosomes—a problem that is prevalent in cancer and can cause miscarriages or disease, such as Down syndrome.

    St. Jude researchers made their discovery by tracking the activity of a small army of molecules that are required to maintain a specialized, tightly packaged form of DNA, called heterochromatin, at the part of the chromosome called the centromere.

    The investigators also showed the order in which certain critical events occur in setting up and maintaining this heterochromatin. The work is important because it gives scientists insight into how each daughter cell receives the normal number of chromosomes; and it offers important clues to understanding the genetic cause of certain catastrophic diseases. A report on this work appears in the May 25 issue of Molecular Cell.

    “Until we did this study, it was virtually impossible to figure out which molecular events were specifically required for the two different processes of establishing and maintaining centromeric heterochromatin,” said Janet Partridge, PhD, Biochemistry. “Now we have the tools to ask what’s required for the cell to perform each task.

    This has important implications not just for understanding how centromeric heterochromatin assembles, but also for learning how heterochromatin forms elsewhere on the chromosome, a process that is often disturbed in cancer.”

    Other authors of this report include Aaron Kosinski, Chemical Biology and Therapeutics; Dagny Ulrich, PhD, Hartwell Center; Michael Hadler, Immunology; and Jennifer DeBeauchamp and Victoria Noffsinger, Biochemistry.

    July 2007