Human special AT-rich sequence-binding protein-1 (SATB1) is a nuclear matrix/scaffold-associated region DNA-binding protein, predominantly expressed in the thymus and pre-B cells.  Like its homolog SATB2, SATB1 selectively binds double-stranded, special AT-rich DNA sequences in which one strand exclusively consists of well-mixed A, T, and C nucleotides.  SATB1 contains a dimerization domain that shares similarity with the PDZ motif, identified as an indispensable element for high-affinity binding of SATB1 to DNA. SATB1 constitutes a functional nuclear architecture that has a 'cage-like' protein distribution surrounding heterochromatin and regulates gene expression through chromatin remodeling/HDAC (histone deacetylase complex) and transcription factors recruitment.  SATB1 functions as a 'genome organizer' essential for proper T-cell development. Recent studies show that SATB1 is necessary for breast cancer cells to become metastatic, and when ectopically expressed in non-metastatic cells, can induce invasive activity in vivo. At least two isoforms of SATB1 are known to exist.