In Science this week, researchers from Uppsala University and the University of California, Davis, propose a new model by which genes evolve new functions. While gene duplication — a process wherein new genes capable of acquiring mutations spring from a redundant copy of a duplicated parental gene — is one way, the investigators offer an innovation-amplification-divergence model where a new gene function arises before duplication and "functionally distinct new genes evolve under continuous selection." Using Salmonella enterica, the team showed that a gene can evolve a new enzymatic function in fewer than 3,000 generations.
And in ScienceExpress, a Rutgers University team reports the three-dimensional structure of the transcription initiation complex, which is composed of the enzyme RNA polymerase and the initiation factor sigma, from the bacterium Thermus thermophilus. They further show how this complex recognizes DNA binding sites, unwinds the DNA helix, and pre-organizes it for subsequent reactions. According to the researchers, "the structures provide a foundation for understanding transcription initiation and transcriptional regulation."
Over in Science Translation Medicine, a multi-institute team led by researchers from Duke-NUS Graduate Medical School in Singapore publish data detailing the role of methylation in gastric cancer. Analyzing genome-wide CG dinucleotide methylation profiles of 240 gastric cancers and 94 matched controls, the investigators identified cancer-specific epigenetic alterations in 44 percent of CpGs, with 25 percent of these "significantly associated" with changes in tumor gene expression. They also found a CpG island methylator phenotype, or CIMP, subgroup associated with "widespread hypermethylation, young patient age, and adverse patient outcome in a disease stage-independent manner." The team also notes that H. pylori infection is a risk factor for gastric cancer, and that the bacterium also increases DNA methylation alterations in infected cells, suggesting an association between environmental and biological factors on gastric cells.