Kruidenier et al. reply.

©2014 Macmillan Publishers Limited. All rights reserved. Replying to B. Heinemann. Nature 514, http://dx.doi.org/10.1038/nature13688 (2014) We welcome the accompanying Comment by Heinemann et al., in which the authors use an extensive panel of sensitive KDM assays to independently confirm our results that GSK-J1 is a potent KDM6 inhibitor. Additionally, Heinemann et al. demonstrate that GSK-J1 has some, albeit weaker, activity towards KDM5B and KDM5C, for which we only had preliminary data available at the time of our original publication. As our jumonji assay portfolio expands, we have continued to update the GSK-J1 activity profile on the SGC website (http://www.thesgc.org/chemical-probes/GSKJ1); this includes KDM5 inhibition activity by GSK-J1 similar to that reported by Heinemann. In conclusion, GSK-J1 remains the most selective KDM inhibitor yet disclosed and thus a valuable chemical tool.