Nat. Chem. Biol. 12, 452–458 (2016); received 16 December 2015; accepted 24 March 2016; published online 25 April 2016; corrected after print 28 June 2016

In the version of this article initially published, the author omitted some funding sources: NIH (R03 DA034602-01A1, R01 CA129105, R01 CA103866, and R37 AI047389 to D.M.S.) and the US Department of Defense (W81XWH-14-PRCRP-IA to D.M.S.). The error has been corrected in the HTML and PDF versions of the article.