Biomaterial Database

The structure of sub-nucleosomal particles. The octameric (H3/H4)4--125-base-pair-DNA complex. 1985

C M Read, and C Crane-Robinson

Chicken erythrocyte chromatin was depleted of histones H1, H5, H2A and H2B. The resulting (H3/H4)-containing chromatin was digested with micrococcal nuclease to yield monomer, dimer, trimer etc. units, irregularly spaced on the DNA, with even-number multimers being more prominent. Sucrose density gradient centrifugation separated monomers and dimers (7.7 S and 10.5 S). Sodium dodecyl sulphate gel electrophoresis and cross-linking indicated: the monomer contains 50-base-pair (bp), 60-bp and 70-bp DNA and the dimer 125-bp DNA; the monomer contains a tetramer and the dimer an octamer of H3 and H4. Partial association of monomer units to dimers inhibits structural studies of monomers. The internal structure of the dimer, i.e. and (H3/H4)4-125-bp-DNA particle, was studied using circular dichroism, thermal denaturation and nuclease digestion. Both micrococcal nuclease and DNase I digestion indicate that, unlike core particles, accessible sites occur in the centre of the particle and it is concluded that the (H3/H4)4-125-bp-DNA particle is not a 'pseudo-core particle' in which the 'extra' H3 and H4 replace H2A and H2B. It is proposed that the octamer particle is formed by the sliding together of two 'monomer' units, each containing the (H3/H4)2 tetramer and 70 bp of DNA. Excision of this dimer unit with micrococcal nuclease results in the loss of 10 readily digestible base pairs at each end, leaving 125 bp.

UI	MeSH Term	Description	Entries
D008836	Micrococcal Nuclease	An enzyme that catalyzes the endonucleolytic cleavage to 3'-phosphomononucleotide and 3'-phospholigonucleotide end-products. It can cause hydrolysis of double- or single-stranded DNA or RNA. (From Enzyme Nomenclature, 1992) EC 3.1.31.1.	Staphylococcal Nuclease,TNase,Thermonuclease,Thermostable Nuclease,Nuclease, Micrococcal,Nuclease, Staphylococcal,Nuclease, Thermostable
D009707	Nucleosomes	The repeating structural units of chromatin, each consisting of approximately 200 base pairs of DNA wound around a protein core. This core is composed of the histones H2A, H2B, H3, and H4.	Dinucleosomes,Polynucleosomes,Dinucleosome,Nucleosome,Polynucleosome
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D011489	Protein Denaturation	Disruption of the non-covalent bonds and/or disulfide bonds responsible for maintaining the three-dimensional shape and activity of the native protein.	Denaturation, Protein,Denaturations, Protein,Protein Denaturations
D002498	Centrifugation	Process of using a rotating machine to generate centrifugal force to separate substances of different densities, remove moisture, or simulate gravitational effects. It employs a large motor-driven apparatus with a long arm, at the end of which human and animal subjects, biological specimens, or equipment can be revolved and rotated at various speeds to study gravitational effects. (From Websters, 10th ed; McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
D002645	Chickens	Common name for the species Gallus gallus, the domestic fowl, in the family Phasianidae, order GALLIFORMES. It is descended from the red jungle fowl of SOUTHEAST ASIA.	Gallus gallus,Gallus domesticus,Gallus gallus domesticus,Chicken
D002843	Chromatin	The material of CHROMOSOMES. It is a complex of DNA; HISTONES; and nonhistone proteins (CHROMOSOMAL PROTEINS, NON-HISTONE) found within the nucleus of a cell.	Chromatins
D002942	Circular Dichroism	A change from planar to elliptic polarization when an initially plane-polarized light wave traverses an optically active medium. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Circular Dichroism, Vibrational,Dichroism, Circular,Vibrational Circular Dichroism
D003850	Deoxyribonuclease I	An enzyme capable of hydrolyzing highly polymerized DNA by splitting phosphodiester linkages, preferentially adjacent to a pyrimidine nucleotide. This catalyzes endonucleolytic cleavage of DNA yielding 5'-phosphodi- and oligonucleotide end-products. The enzyme has a preference for double-stranded DNA.	DNase I,Streptodornase,DNA Endonuclease,DNA Nicking Enzyme,DNAase I,Dornavac,Endonuclease I,Nickase,Pancreatic DNase,T4-Endonuclease II,T7-Endonuclease I,Thymonuclease,DNase, Pancreatic,Endonuclease, DNA,T4 Endonuclease II,T7 Endonuclease I
D004912	Erythrocytes	Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.	Blood Cells, Red,Blood Corpuscles, Red,Red Blood Cells,Red Blood Corpuscles,Blood Cell, Red,Blood Corpuscle, Red,Erythrocyte,Red Blood Cell,Red Blood Corpuscle