Modulation of histone H5-nucleosome interactions by H5 phosphorylation

1982

Studies in vitro of binding high‐mobility‐group (HMG) proteins to nucleosomal particles that differ in their DNA contents reflect several aspects pertinent to their function in vivo. Two molecules of HMG 14 or 17 are accomodated by particles with 140 or 180 base pairs of DNA whereas HMG 1 or 2 are only bound by the larger specimens irrespective of the presence of HMG 14/17. It is concluded that one molecule of HMG 1 or 2 binds to the 40 base pairs of linker DNA whereas the HMG 14 or 17 molecules associate with the nucleosomal core. At physiological ionic strength, HMG 14 binding is cooperative, probably by triggering a conformational change in the nucleosomal particle. The phenomenon has been studied by two independent techniques. Besides the common gel‐electrophoretic system, a centrifugation assay is described, which permits the derivation of a Hill coefficient nH= 1.3 and dissociation constants in the range of 30–90 nM at 0.15 M NaCl, pH 6.8.

Section: Discussionmentioning

confidence: 99%

The Binding Sites for Large and Small High‐Mobility‐Group (HMG) Proteins

Schröter

1982

“…The entire suspension was layered on the top of a freshly packed column with 5rnl Bio-Gel A5m and eluted at the same ionic strength. The emerging monomeric fractions were free from the linker histone (Hl) as it binds preferentially and cooperatively to the higher-molecular-weight species at quasiphysiological ionic strength [10,16]. In cases where some turbidity emerged near the void volum it was easily removed by centrifugation.…”

Section: Preparation Of Chinese Humster Ovary Core Particlesmentioning

confidence: 99%

“…(a) H1 (H5) is the only histone which can directly be displaced by protamine from calf thymus [42] and chicken erythrocyte nuclei [43] or from the corresponding chromatins [5,42]. (b) The nucleosomal entity provides a perfect protection of the core histones from protamic in nuclei, chromatin and core particles [5,16,42]. (c) A chemical acetylation of calf thymus chromatin does not support the replacement of the Fig.…”

Section: The Interaction Of Core Purticies and Protarninesmentioning

confidence: 99%

Modulation of the Nucleosome Structure by Histone Acetylation

Henco

Wingender

1980

A rapid procedure for the isolation of core particles from Chinese hamster ovary cells is described which permits measurements, usually at the day of their preparation. Particles of 145 f 5 base pairs, derived from interphase cells, will be compared with the analogue specimens from butyrate-treated cells, metaphase cells and a standard preparation from chicken erythrocytes. Butyrate cause an increase in the acetylation of histones H3 and H4, which induces alterations of the interhistone and histone-DNA interactions. Changes in the interhistone contacts, correlated to an extension of a-helical segments, lead to an altered accessibility of the H3 cysteine side-chains and to a different histone displacement by protamines. On the other hand, histone-DNA contacts are loosened in parts and this is particularly evident from the changes in the premelting region of a thermaldenaturation profile.In the structural element of chromatin two each of histones H2a, H2b, H3 and H4 form an octameric protein core which is surrounded by a 140-base-pair segment of DNA. These 'core particles' are linked by a variable segment of DNA to reveal a repeating subunit structure (nucleosome) [l]. Specific lysine side-chains within the highly basic aminoterminal regions of histone H3 (residues 9, 14, 18 and 23) and histone H4 (residues 5, 8, 12 and 16)

“…This step excises those regions from the oligomers that have become HI-free due to its cooperative rebinding during the first saltinduced fractionation (cf. [17]). At the end of this second digestion, [30][31][32][33][34][35][36][37][38][39][40] of the input chromatin is rendered soluble in supernatant 2.…”

Section: Preparation and Ckaracterization Of Hjyeracetylated Nucleosomentioning

confidence: 99%

“…1). In principle, this protocol exploits the preferential and highly cooperative binding of the linker histone (HI) to oligomeric and the larger monomeric particles [13,17] permitting the separation into a soluble, HI-free supernatant and a HI-enriched pellet at 0.15 M NaC1. Protein analyses show that monomers of this first supernatant still contain some nonhistone proteins, most prominently the small H M G proteins 14 and 17 at an average molar ratio of 0.5 HMG/particle (Fig.…”

Section: Preparation and Ckaracterization Of Hjyeracetylated Nucleosomentioning

confidence: 99%

Nucleosomal Particles Open as the Histone Core Becomes Hyperacetylated

Gómez-Lira

Schröter

1983

Lymphoblastoid cells grown in the presence of the deacetylase inhibitor butyrate were used to isolate nucleosomal particles in a hyperacetylated state. During a non‐denaturing gel electrophoresis these particles revealed a heterogeneity which is only in part due to the presence of nonhistone proteins. Monomers that are free from histone H1 and high‐mobility‐group (HMG) proteins 14 and 17 yield a subfractionation according to the degree of core histone acetylation beyond a limiting value of 10 acetyl groups/particle. It is shown that hyperacetylation provides particles with low mobilities and a considerable conformational freedom in contrast to HMG protein 14 which locks them in a conformation that has a similar electrophoretic behaviour but is more defined.