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

Journal Article · Fri Jan 01 04:00:00 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), Journal Name: Biochemistry; (United States) Vol. 21; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

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