Correction to: Nature https://doi.org/10.1038/nature13234 Published online 4 May 2014

In the version of this article initially published, due to a figure preparation error, in the lower panel of Extended Data Fig. 6b, the Mcm5 IP sample was inserted twice (once as the IP and again as the extract), rather than the relevant Mcm5 extract sample. Due to the age of the article, Extended Data Fig. 6 cannot be replaced directly; the Supplementary information published with the online version of this amendment serves to update the figure.

Supplementary information is available in the online version of this amendment.