Nature Reviews Molecular Cell Biology 11, 607–620 (2010)

On page 610 of the above article there is a mistake in BOX 1: HsK27me3 should be H3K27me3. On page 616 there is a mistake in FIG. 6. The arrow concerning 5′-dA between step 1 and step 2 should be pointing in the other direction, as shown here. We apologize for any confusion caused to readers.