The superhelical density of nuclear DNA from human cells.

Structures resembling nuclei may be released by gently lysing human cells in solutions containing non-ionic detergents and high concentrations of salt. These structures, which we call nucleoids, sediment in sucrose gradients containing the intercalating agent, actinomycin D, in the manner characteristic of superhelical DNA. We have determined the concentration of actinomycin that minimises the rate of sedimentation of nucleoids. At this concentration, we have determined the amount of drug bound per base pair of DNA by means of a double-labelling procedure. Assuming that each molecule of actinomycin bound to nucleoid DNA unwinds the double helix by 26 degrees, we calculate that there is one supercoil every 90-180 base pairs in nucleoid DNA. These values lie within the range found for the circular DNA molecules of plasmids and viruses.

[1]  P. Cook,et al.  Characterization of nuclear structures containing superhelical DNA. , 1976, Journal of cell science.

[2]  P. Cook,et al.  Conformational constraints in nuclear DNA. , 1976, Journal of cell science.

[3]  P. Cook,et al.  Detection and repair of single-strand breaks in nuclear DNA , 1976, Nature.

[4]  J. Vinograd,et al.  The number of superhelical turns in native Virion SV40 DNA and Minicol DNA determined by the band counting method , 1976, Cell.

[5]  P. Cook,et al.  Supercoils in human DNA. , 1975, Journal of cell science.

[6]  P. Chambon,et al.  Folding of the DNA double helix in chromatin-like structures from simian virus 40. , 1975, Proceedings of the National Academy of Sciences of the United States of America.

[7]  J. Griffith.  Chromatin Structure: Deduced from a Minichromosome , 1975, Science.

[8]  D. E. Olins,et al.  Chromatin fragments resembling v bodies. , 1975, Science.

[9]  D. Pulleyblank,et al.  The sense of naturally occurring superhelices and the unwinding angle of intercalated ethidium. , 1975, Journal of molecular biology.

[10]  J. Wang.  The degree of unwinding of the DNA helix by ethidium. I. Titration of twisted PM2 DNA molecules in alkaline cesium chloride density gradients. , 1974, Journal of molecular biology.

[11]  R. Kornberg.  Chromatin structure: a repeating unit of histones and DNA. , 1974, Science.

[12]  J. Vinograd,et al.  A buoyant method for the determination of the superhelix density of closed circular DNA. , 1971, Journal of molecular biology.

[13]  J. Vinograd,et al.  Sedimentation velocity behavior of closed circular SV40 DNA as a function of superhelix density, ionic strength, counterion and temperature. , 1971, Journal of molecular biology.

[14]  M. Waring,et al.  Variation of the supercoils in closed circular DNA by binding of antibiotics and drugs: evidence for molecular models involving intercalation. , 1970, Journal of molecular biology.

[15]  W. Bauer,et al.  Interaction of closed circular DNA with intercalative dyes. II. The free energy of superhelix formation in SV40 DNA. , 1970, Journal of molecular biology.

[16]  H. J. Li,et al.  Relaxation studies of the proflavine-DNA complex: the kinetics of an intercalation reaction. , 1969, Journal of molecular biology.

[17]  W. Bauer,et al.  The interaction of closed circular DNA with intercalative dyes. I. The superhelix density of SV40 DNA in the presence and absence of dye. , 1970, Journal of molecular biology.

[18]  A. Peacocke,et al.  The interaction of aminoacridines with nucleic acids , 1968, Hoppe-Seyler's Zeitschrift fur physiologische Chemie.

[19]  D M Crothers,et al.  Studies of the binding of actinomycin and related compounds to DNA. , 1968, Journal of molecular biology.

[20]  M. Waring,et al.  Complex formation between ethidium bromide and nucleic acids. , 1965, Journal of molecular biology.

[21]  M. Waring,et al.  A Molecular Model for the Interaction of Ethidium Bromide with Deoxyribonucleic Acid , 1964 .

[22]  R. Haselkorn.  Actinomycin D as a Probe for Nucleic Acid Secondary Structure , 1964, Science.

[23]  W. Fuller,et al.  X-Ray Diffraction and Molecular Model Building Studies of The Interaction of Actinomycin with Nucleic Acids , 1963, Nature.