Correction to: Nature https://doi.org/10.1038/s41586-019-1259-3, published online 29 May 2019.

In this Article, owing to errors during the production process, in Fig. 1a, the 5′ and 3′ labels at the right-hand side of the DNA sequence were reversed, and the top strand should therefore run 5′ to 3′ (and the bottom strand 3′ to 5′). In addition, Fig. 4 was missing the panel labels ‘a–e’. These errors have been corrected online.