Nature Reviews Genetics (2019) https://doi.org/10.1038/s41576-019-0135-1 Published online 03 June 2019

In figures 1, 4 and 5 of this article there were several instances where the transcribing RNA polymerase II (and the RNA–DNA hybrid inside it) had the incorrect left–right orientation. These figures have now been corrected. Additionally, minor text errors in the main text have been corrected: in the section “Nascent RNAs in gene regulation”, the phrase “histone shock gene” has been corrected to “heat shock gene”, and “chromatin spreading” has been updated specifically to “heterochromatin spreading” when discussing the functions of Xist-interacting proteins.