Solution structure of the SWIRM domain of human histone demethylase LSD1

SWIRM is an evolutionarily conserved domain involved in several chromatin-modifying complexes. Recently, the LSD1 protein, which bears a SWIRM domain, was found to be a demethylase for Lys4-methylated histone H3. Here, we report a solution structure of the SWIRM domain of human LSD1. It forms a compact fold composed of 6 alpha helices, in which a 20 amino acid long helix (alpha 4) is surrounded by 5 other short helices. The SWIRM domain structure could be divided into the N-terminal part (alpha 1-alpha 3) and the C-terminal part (alpha 4-alpha 6), which are connected to each other by a salt bridge. While the N-terminal part forms a SWIRM-specific structure, the C-terminal part adopts a helixturn-helix (HTH)-related fold. We discuss a model in which the SWIRM domain acts as an anchor site for a histone tail.