Interestingly, other APL fusion proteins PLZF-RARα and NPM-RARα also activated transcription by HIF-1α upon stabilization by the hypoxia-mimetic agent cobalt chloride (CoCl2, which at the conditions used in our assays induced HIF-1α and not HIF-2α transcriptional activity, Supplementary Fig S1D and E), while fusion proteins of other AML sub-types such as AML1-ETO did not (Fig 1D). Here, NPM1 is linked to acute myeloid leukemia.