Ingolia, N.T. et al. Cell 147, 789–802 (2011).

Evidence is accumulating that most of the mammalian genome is not only transcribed but more transcripts than anticipated are actively translated. Ingolia et al. recently adapted established methods to study the dynamics and complexity of mammalian proteomes. By deep-sequencing RNA fragments protected by ribosomes, they obtained a map of genome-wide protein synthesis; stalling the ribosomes at sites of initiation followed by run-off elongation allowed them to investigate the kinetics of translation. In mouse embryonic stem cells the researchers found many unannotated open reading frames and short translation products in the vicinity of long noncoding RNAs. A catalogue of these translation products is the first step toward exploring their function.