In a Cell paper published online in advance this week, an international team led by investigators at Children's Hospital Boston shows that "the RNA exosome targets the AID [activation-induced cytidine deaminase ] … to both strands of transcribed duplex DNA substrates." More specifically, the authors write, the RNA exosome "accumulates on IgH switch regions in an AID-dependent fashion," a process that is "required for optimal" class switch recombination.