In Science this week, an international team of researchers report new data showing that 3' transductions mediated by long interspersed nuclear element–1 (L1) retrotransposons — mobile repetitive elements found throughout the human genome — are present in many cancer genomes. Looking at the cancer genomes of 244 patients, the scientists discovered that tumors from 53 percent of the patients had somatic retrotranspositions, of which 24 percent were 3' transductions. Fingerprinting of donor L1s revealed that a few of source L1 elements in a tumor could arise from tens to hundreds of 3' transductions, which can themselves seed further retrotranspositions. Additionally, the activity of individual L1 elements fluctuated during tumor evolution and correlated with L1 promoter hypomethylation.
Also in Science, two University of Copenhagen researchers discuss how studies of ancient genomes, with a focus on epigenetic changes, can reveal regulatory changes that underlie species divergence and population adaptation. They review the results of previous research efforts and predict that technological advances may help overcome the challenges currently facing the field. They also stress the importance of investigating ancient epigenomes despite the difficulties in interpreting results from such efforts.