Life's instructions are written in DNA, but it is the enzyme RNA polymerase II (Pol II) that reads the script, transcribing RNA in eukaryotic cells and eventually giving rise to proteins. Scientists know that Pol II must advance down the gene in perfect sync with other biological processes; aberrations in the movement of this enzyme have been linked to cancer and aging. But technical hurdles prevented them from precisely determining how this important molecular machine moves along DNA, and what governs its pauses and accelerations.
