Phosphorylation induces sequence-specific conformational switches in the RNA polymerase II C-terminal domain

The RNA polymerase II C-terminal domain acts as a hub to coordinate transcription and nascent mRNA processing. Here the authors identify a phosphorylation-dependent switch in the trans-to-cis isomerization of proline in the CTD heptad repeats that make those repeats susceptible to further modifications by regulatory enzymes.