Interferon regulatory factor 1 (IRF-1) is an essential factor involved in the regulation of type I interferon (IFN) and IFN-inducible genes. The protein consists of 329 amino acids that are highly conserved from mouse to human. Similar to other transcription factors, the protein is modular in nature with a basic N-terminal region involved in DNA binding and an acidic C-terminal region required for activation. We report here the expression, purification and co-crystallization of the minimal N-terminal region of IRF-1 involved in DNA binding (amino acids 1–113) with a 13 bp DNA fragment from the IFN-β promoter. The crystals diffract to at least 3.0Åin resolution and belong to space group R3 with unit cell parameters of a = b = 84.8Å, c = 203.7Å.
