We previously identified a MAR-binding protein, SATB1. SATB1 consists of a novel class of DNA-binding proteins recognizing a specific region with the high unwinding capability (BUR; base unpairing region) typically found in MARs. SATB1 is a cell-type specific MAR-binding protein, which is predominantly expressed in thymocytes. SATB1 binds in vivo in thymocytes and Jurkat T cells to specialized genomic DNA at the bases of chromatin loop domains, the sites that are attached to the nuclear matrix.

We demonstrated that SATB1 is an essential protein for proper T-cell development, by establishing SATB1 knockout mice. In SATB1-deficient thymocytes, multiple genes are dysregulated. We are also currently studying the role of SATB1 in T-cell apoptosis. BUR sequences are binding targets of other MAR-binding proteins. We have characterized a series of such proteins from human breast carcinomas. The MAR-binding activity of these proteins was virtually undetectable in normal breast tissues and in benign breast lesions but it was strongly detectable in all breast carcinomas tested. Our recent study shows that certain proteins from human breast carcinomas make a protein complex and synergistically bind to BURs. Some MAR-binding proteins may be critical for the maintenance of breast cancer or other types of cancer. Further research on these proteins may provide important insights to cancer therapy in the future.