Topo II (pink) is localized to the axes of mitotic chromosomes.
When William Earnshaw struck out from his postdoc with Ulrich Laemmli for his new lab at Johns Hopkins University (Baltimore, MD) in 1981, he took with him Laemmli's rather controversial idea that a chromosome scaffold of nonhistone proteins might be responsible for the radial loop structure of chromatin. Laemmli's studies of metaphase chromosomes, which had been depleted of histones, supported such a model (Paulson and Laemmli, 1977; Marsden and Laemmli, 1979).
At Hopkins, Earnshaw soon learned, “people used antibodies for everything,” so he followed suit. After eight months spent isolating human chromosomes, digesting the DNA, then extracting away the more soluble proteins, he had three presumptive scaffold protein bands with which to immunize guinea pigs. Paranoid, he spray painted dots on the guinea pigs' backs so as not to lose track of them (it...
