HMGA1, an 11 kDa basic, DNA-binding non-histone nuclear protein, is a key member of HMGA protein family. It consists of a highly conserved AT-hook DNA-binding 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. It is involved in many cellular processes including growth regulation, viral induction of beta-IFN gene and regulation of inducible gene transcription. It also physically interacts with transcription factors such as AP-1, Sp-1 and CAAT/enhancer binding protein-beta to modulate their ability to activate gene expression. It functions as a direct transcriptional target of c-Jun and c-Myc and is maximally expressed during embryonic development. Pathological role of HMGA1 include integration of retroviruses into chromosomes and enhancing metastasis of tumor cells.