Autoradiograph of the gel shift assay through which Prof. Gregg Semenza with his research group identified hypoxia-inducible factor 1. The original autoradiograph is now in the Nobel Prize Museum in Stockholm. Lanes 1 and 2 contain a DNA fragment from the hypoxia-response element. Lanes 3 and 4 contain the same DNA fragment with a three base-pair change which eliminates the ability of the HRE to direct hypoxia-induced gene expression. The big arrow points to a band that is present in Lane 1 but not in any other lane. This is hypoxia-inducible factor 1. Reprinted from Semenza¹ with permission from Elsevier Inc.