BD Transduction Laboratories™ Purified Mouse Anti-ICBP90

DNA topoisomerases are ubiquitous nuclear enzymes that alter the topology of DNA. Topoisomerase I produces transient single-stranded breaks in DNA, while topoisomerase II produces transient double-stranded breaks in DNA. These DNA breaks are important for DNA replication and chromosome condensation and segregation. Two types of topoisomerase II have been identified, TopoIIα and TopoIIβ. During interphase, TopoIIα is found in the nucleoplasm and nucleoli, and in mitosis, TopoIIα is found associated with metaphase chromosomes and centromeres. Transcriptional control of TopoIIα expression is regulated through multiple gene promoters, which include five inverted CCAAT boxes, one ATF binding sequence, and two GC-rich boxes. ICBP90 was identified in one-hybrid screen of proteins that can bind an inverted CCAAT box. ICBP90 is expressed highest in proliferative tissues such as thymus, liver, and bone marrow. Overexpression of ICBP90 in COS-1-transfected cells leads to enhanced expression of TopoIIα. ICBP90 co-localizes with TopoIIα in proliferating areas of appendix and in high grade breast carcinomas. Thus, ICBP90 may be an important transcripitonal regulator of TopoIIα expression in proliferating cells.