Subnucleosomes and their relationships to the arrangement of histone binding sites along nucleosome deoxyribonucleic acid

Journal Article · Fri Jan 01 00:00:00 EST 1982 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00261a026· OSTI ID:5687750

Nelson, D A ^[1]; Mencke, A J; Chambers, S A; Oosterhof, D K; Rill, R L

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1. Florida State Univ., Tallahassee

Micrococcal nuclease cleaves within nucleosomes at sites spaced about 10.4 base pairs (bp) apart. Cleavages at sites equivalent to 30-35 bp from the ends of 146-bp cores cause spontaneous loss of an H2a-H2b pair associated with 30-40 bp length DNA. Cleavages at certain other sites do not affect the nucleosome integrity unless a solvent perturbant such as urea is added. Chromatin moderately digested with micrococcal nuclease, when fractionated by sedimentation or electrophoresis in the presence of 3 M urea, yielded four previously unobserved subnucleosomes with the following histone/DNA compositions: (H3)/sub 2/(H4)/sub 2/(H2a)(H2b)/95-115 bp; (H3)(H4)/70-80 bp DNA; (H2a)(H2b)/50-60 bp DNA; and (H1)/60-70 bp DNA. All but the latter subnucleosome were also obtained upon DNase I digestion of purified nucleosome cores labeled on the 5' ends with /sup 32/P. Only subnucleosomes that retained H2a and H2b also retained labeled ends. These results show that H2a and H2b are paired on the terminal 30-40 bp of core DNA, as suggested from analyses of histone-DNA cross-link products by Mirzabekov and coworkers. Considerations of the orgins and compositions of subnucleosomes and of cross-linking data suggest an expanded model for the locations of histone binding sites along nucleosome core DNA. The principal features of this model are (i) strong electrostatic binding sites of H2a and H2b occur at positions approximately 20-30 bp from the core ends, (ii) strong electrostatic binding sites of H3 and H4 occur primarily on the central 40 bp of core DNA, (iii) strong nonelectrostatic, urea-sensitive binding sites of H3 and H4 occur at positions approximately 30-50 bp from the core ends, and (iv) urea-sensitive binding sites of H2a or H2b may occur on the terminal 10-20 bp of core DNA.

• OSTI ID: 5687750
• Journal Information: Biochemistry; (United States), Vol. 21
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
DNA
STRUCTURAL CHEMICAL ANALYSIS
HISTONES
CHEMICAL BONDS
NUCLEOSOMES
CHEMICAL COMPOSITION
CHROMATIN
CROSS-LINKING
ELECTROPHORESIS
FRACTIONATION
LABELLED COMPOUNDS
MICROCOCCUS
PHOSPHORUS 32
TRACER TECHNIQUES
BACTERIA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MICROORGANISMS
NUCLEI
NUCLEIC ACIDS
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PHOSPHORUS ISOTOPES
POLYMERIZATION
PROTEINS
RADIOISOTOPES
SEPARATION PROCESSES
550201* - Biochemistry- Tracer Techniques