Guardian of the Genome, Tumor Suppressor p53, Restrains Movement of Retrotransposons; Mutated p53 Permits Much-Increased Movement of Retrotransposons, Leading to Tumor Formation

The most commonly mutated gene in cancer, p53, works to prevent tumor formation by keeping mobile elements in check that otherwise lead to genomic instability, University of Texas (UT) Southwestern Medical Center researchers have found. The p53 gene has long been known to suppress tumor formation, but the mechanisms behind this function - and why disabling the gene allows tumors to form - were not fully understood. Findings from the new study, published online on December 23, 2015 in Genes & Development, answer some of these questions and could one day lead to new ways of diagnosing and treating cancer, said the study's senior author, Dr. John Abrams, Professor of Cell Biology at UT Southwestern. The investigators found that normal p53 gene action restrains transposons, mobile genetic elements called retroelements that can make copies of themselves and move to different positions on chromosomes. But, they discovered, when p53 is disabled by mutation, dramatic eruptions of these mobile elements occur. The study revealed that in mice with cancer and in human samples of two types of cancer (Wilms' tumors and colon tumors) disabled for p53, transposons became very active. In a healthy state, certain mechanisms work to keep these retroelements quiet and inactive, explained Dr. Abrams. One of those mechanisms is p53 action. Conversely, when p53 is mutated, retroelements can erupt. "If you take the gene away, transposons can wreak havoc throughout the genome by causing it to become highly dysregulated, which can lead to disease," Dr. Abrams said. "Our findings help explain why cancer genomes are so much more fluid and destabilized than normal genomes. They also provide a novel framework for understanding how normal cells become tumors." Although much more research is needed, Dr.
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