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Journal of Cell Science, Vol 29, Issue 1 103-116, Copyright © 1978 by Company of Biologists
JOURNAL ARTICLES |
JM Levin, E Jost and PR Cook
Structures retaining many of the morphological features of nuclei may be released by gently lysing human cells in solutions containing non-ionic detergents and high concentrations of salt. These nucleoids contain superhelical DNA. Using a double-labelling procedure we have compared, at different salt concentrations, the amounts and types of protein associated with human nucleoides containings superhelical or relaxed DNA. We find that the slightly lysine-rich histones (H2A and H2B) but not the arginine-rich histones (H3 and H4) dissociate more slowly from nucleoids containing superhelical DNA than from those containing relaxed DNA. A protein of apparent molecular weight of 22000 also binds more tightly to superhelical DNA. We conclude that this protein and the slightly lysine-rich histones transmute free energy of supercoiling into binding energy when they bind to superhelical DNA.