Histones bind more tightly to bromodeoxyuridine-substituted DNA than to normal DNA

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Abstract
Using a membrane filter assay, we have obtained results from both kinetic and competition experiments indicating that histones bind more strongly to bromodeoxyuridine-substituted DNA than to normal DNA. At 37° C in our standard buffer of 0.2 M ionic strength, the rate of dissociation of histones HI, H2, and H4 from BrdU-substituted DNA is respectively 7, 4, and 2 times slower than it is from normal DNA. Competition experiments show an even greater difference between BrdU-substituted and normal DNA with respect to histone binding. The tighter binding of histones to BrdU-substituted DNA is of interest because of the known effects of BrdU on eukaryotic chromosome condensation and staining, virus induction, and the inhibition of differentiation.