Organisms with the wrong number of chromosomes often die or have growth abnormalities, yet most cancers have the same error and thrive. To figure out how cancer cells overcome this growth disadvantage, Angelika Amon at the Massachusetts Institute of Technology in Cambridge and her colleagues analysed the genomes of 14 yeast strains with extra chromosomes and higher growth rates. The researchers teased out a mutation in a gene coding for an enzyme known as Ubp6. This enzyme normally works to remove a molecule called ubiquitin from proteins, preventing the proteins from being degraded in the cell.
The researchers found that some strains with the Ubp6 mutation proliferated faster than similar ones without the mutation. These strains also had protein compositions that were closer to those of normal yeast cells than were those of strains without the mutation, suggesting that the Ubp6 mutants degrade the excess proteins generated by their extra chromosomes.