High mobility group protein HMG-I/HMG-Y, also known as HMGA1, is a member of the non-histone chromosomal high mobility group protein (HMG) family. HMGA1 consists of a highly conserved AT-hook DNAbinding domain that mediates binding to AT-rich sequences in the minor groove of chromosomal DNA. It functions as architectural chromatin-binding transcription factor altering the conformation of DNA by modulating nuclear protein-DNA complexes.