Topoisomerase II Binding Protein 1 (TOPBP1)

TOPBP1 is a binding protein which interacts with the C-terminal region of topoisomerase II beta. This interaction suggests a supportive role for this protein in the catalytic reactions of topoisomerase II beta through transient breakages of DNA strands.The deduced 1,522-amino acid protein has a calculated molecular mass of about 171 kD. TOPBP1 contains 8 repeating regions throughout its sequence that share similarity with repeat regions 1 and 2 of Rad4. It also has an auto-ADP-ribosylation site and 2 C-terminal nuclear localization signals. The 3-prime untranslated region contains 12 AUUUA mRNA-instability motifs. Northern blot analysis detected ubiquitous expression, with smearing characteristic of unstable mRNA. Transcripts above 10 kb were detected only in heart.