June 28, 2002 -- Researchers have identified how a form of lymphoma develops when large pieces of chromosomes swap locations. Their observations about how chromosome rearrangements, or translocations, cause pro-B cell lymphoma in mice offer a fresh perspective on how cancers arise from an increased "dosage" of specific genes or regions of the genome.

The studies are reported in the June 28, 2002, issue of the journal Cell by Howard Hughes Medical Institute (HHMI) investigator Frederick W. Alt, HHMI associates Chengming Zhu and Kevin D. Mills, and colleagues at Children's Hospital in Boston, Harvard Medical School, the Center for Blood Research, and Brigham and Women's Hospital.

Leukemias and lymphomas can arise when chromosomes inappropriately swap genetic material. After the genetic material is swapped, various genes are removed from their natural context and they propel cell growth because they are no longer under normal control. In some cases, more complex gene translocations (as opposed to swapping one gene for another) lead to amplification of large regions of the genome. Alt and his colleagues coined the term "complicon" -- derived from "complex translocation" -- to describe this phenomenon.

Complicons may develop when the cell's DNA repair mechanisms malfunction. When DNA repair fails, broken chromosomes can persist and recombine inappropriately with other chromosomes. This leads to chromosomal translocations where genes or whole chunks of the genome are swapped from one chromosome to another.

"Complicons are commonly seen in human carcinomas, in which very complex rearrangements cause two genes that are normally on different chromosomes to amplify together," said Alt. "To date, however, there have been no mechanistic studies that have shown how complicons arise."

Alt and his colleagues, who have been studying a specific type of DNA repair pr
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
27-Jun-2002

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