The histone core exerts a dominant constraint on the structure of DNA in a nucleosome.
We have examined the structures of unique sequence, A/T-rich DNAs that are predicted to be relatively rigid [oligo(dA).oligo(dT)], flexible [oligo[d(A-T)]], and curved, using the hydroxyl radical as a cleavage reagent. A 50-base-pair segment containing each of these distinct DNA sequences was placed adjacent to the T7 RNA polymerase promoter, a sequence that will strongly position nucleosomes. The final length of the DNA fragments was 142 bp, enough DNA to assemble a single nucleosome. Cleavage of DNA in solution, while bound to a calcium phosphate crystal, and after incorporation into a nucleosome is examined. We find that the distinct A/T-rich DNAs have very different structural features in solution and helical periodicities when bound to a calcium phosphate. In contrast, the organization of the different DNA sequences when associated with a histone octamer is very similar. We conclude that the histone core exerts a dominant constraint on the structure of DNA in a nucleosome and that inclusion of these various unique sequences has only a very small effect on overall nucleosome stability and structure.
Hayes
J J
JJ
Laboratory of Molecular Embryology, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
Bashkin
J
J
Tullius
T D
TD
Wolffe
A P
AP
D000818:Animals; D001482:Base Composition; D001483:Base Sequence; D001665:Binding Sites; D002645:Chickens; D004247:DNA / Q000737:chemistry*; D006657:Histones / Q000737:chemistry*; D006878:Hydroxides; D017665:Hydroxyl Radical; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009707:Nucleosomes / Q000737:chemistry*; D012996:Solutions
D006657:Histones; D006878:Hydroxides; D009707:Nucleosomes; D012996:Solutions; D017665:Hydroxyl Radical; D004247:DNA