Correction to: Nature https://doi.org/10.1038/nature08820 Published online 7 March 2010
The Editors would like to alert the readers that concerns have been raised regarding the western blot bands in Figs. 1e, 3g, and 4c. Specifically, the ULF bands between lanes 1 and 4 in Fig. 3g, as well as the three ARF bands between lanes 2 and 4 in Fig. 1e and lanes 1 and 3 in Fig. 4c, appear to be very similar. The authors no longer have the original data so the images could not be verified. Readers are advised to interpret these results with caution. Wei Gu has stated on behalf of the authors that they do not agree with this Expression of Concern.