Topoisomerase II is a structural component of mitotic chromosome scaffolds.

TLDR

The authors showed that the 170‑kDa scaffold protein is DNA topoisomerase II by demonstrating that an anti‑scaffold antibody blocks its strand‑passing activity and that both the anti‑scaffold antibody and an independent anti‑bovine topoisomerase II antibody recognize identical proteolytic fragments. A 170‑kDa protein recognized by a polyclonal antibody is a major component of chicken mitotic chromosome scaffolds and is also present in interphase nuclei, suggesting that topoisomerase II serves as a structural protein in both cell cycle stages.

Abstract

We have obtained a polyclonal antibody that recognizes a major polypeptide component of chicken mitotic chromosome scaffolds. This polypeptide migrates in SDS PAGE with Mr 170,000. Indirect immunofluorescence and subcellular fractionation experiments confirm that it is present in both mitotic chromosomes and interphase nuclei. Two lines of evidence suggest that this protein is DNA topoisomerase II, an abundant nuclear enzyme that controls DNA topological states: anti-scaffold antibody inhibits the strand-passing activity of DNA topoisomerase II; and both anti-scaffold antibody and an independent antibody raised against purified bovine topoisomerase II recognize identical partial proteolysis fragments of the 170,000-mol-wt scaffold protein in immunoblots. Our results suggest that topoisomerase II may be an enzyme that is also a structural protein of interphase nuclei and mitotic chromosomes.