Prepartation of soluble chromatin and specific chromatin fractions with restriction nucleases.

By digestion of rat liver nuclei with EndoR HaeIII, EndoR EcoRI, and EndoR Bam and subsequent lysis of the nuclei approx. 90%, 40%, and 45%, respectively, of the chromatin were solubilized. The plateau values of solubilization are in agreement with a model in which the chromatin strands are crosslinked and/or attached to a supporting structure. The distribution of DNA lengths in the soluble and insoluble chromatin fractions were determined. According to digestion experiments with restriction nucleases rat liver DNA contains highly repetitive sequences, some of which are arranged in tandem repeats of 95 and 380 nucleotide pairs, respectively. With EndoR EcoRI chromatin containing the repetitive RNA was preferentially solubilized and, by subsequent sucrose gradient centrifugation, purified to about 90%. The useful properties of chromatin prepared by the specific action of restriction nucleases are discussed.     

Effects of chromatin protein fractions on transcriptional activity of chicken thrombocyte and erythrocyte chromatin

1. Chromatin proteins of chicken thrombocytes and erythrocytes were separated into three fractions by successive extraction with 5 M urea containing various salt concentrations and pH values. Molecular composition of protein fractions was determined by SDS-polyacrylamide gel electrophoresis. 2. The efficiences of the chromatin residues after sequential protein extractions as well as those of reconstituted DNA-protein fraction complexes, in serving as a template for the in vitro RNA synthesis were measured in order to identify the effect of each fraction. 3. The different involvement of chromatin protein fractions of template properties of thrombocyte and erythrocyte chromatin was stated.     

On the heterogeneity of chromatin fractions after gel filtration

Partially salt-extracted nucleoproteins in the eluted fractions after gel filitration in 0.6 to 1.0 m-NaCl are heterogeneous in terms of the protein to DNA ratio. This heterogeneity is due to a redistribution within the gel column of the proteins associated with the DNA. If the fractions of the nucleoprotein peak are pooled before the NaCl is removed, then the resulting material is homogeneous.     

Chicken antichromatin antibodies: specificity to different chromatin fractions.

Specific complement-fixing and precipitin antibodies were induced in chicken to chromatin from WI-38 human diploid fibroblast. Chicken antibodies were chosen because they present two major advantages with respect to rabbit antibodies: (a) the optimal NaCl concentration for chicken precipitin is 1.5 M, which is also an optimal solvent for chromatin proteins that are insoluble at the lower salt concentration required by rabbit precipitin; (b) chicken antichromatin antibodies require an antigen concentration much lower with respect to rabbit antibodies for saturation at the complement-fixation reaction. These antibodies are species specific and they react at the complement-fixation and precipitin assay not only with the whole chromatin but also with dissociated proteins, albeit at a higher concentration of both antigen and antibodies. The specificity of these antibodies to different fractions of chromosomal proteins and of the chromatin after washing with a solution at a different sodium chloride concentration has been investigated.     

Specificity of androgen resistance inMus caroli kidney

Androgen controls the expression of beta-glucuronidase and several other proteins in the kidney of the standard laboratory mouse, Mus musculus. Other species within the genus Mus exhibit a variety of response patterns for kidney beta-glucuronidase and other markers of androgen action. We have investigated the mechanism of androgen action in M. caroli, a Mus species that does not produce beta-glucuronidase in response to testosterone. The failure of testosterone to induce beta-glucuronidase in M. caroli females cannot be overcome by treatment with dihydrotestosterone, with pharmacological doses of testosterone propionate or dihydrotestosterone propionate, or with a variety of potent androgen analogues. All of these compounds induce kidney beta-glucuronidase in M. musculus females and kidney ornithine decarboxylase, submandibular gland renin, and submandibular gland epidermal growth factor in both M. caroli and M. musculus females. Furthermore, kidney androgen receptor proteins from M. caroli and M. musculus animals have the same sedimentation characteristics on sucrose density gradients. These data indicate that androgen resistance in M. caroli is not due to deficient 5 alpha-reductase or aberrant hormone metabolism producing suboptimal levels of functional androgen and is not caused by a defective androgen receptor. They suggest that the resistance of beta-glucuronidase in M. caroli kidney to induction by androgen occurs at the level of the beta-glucuronidase gene.     

X-linked glucose-6-phosphate dehydrogenase deficiency inMus musculus

A mouse with X-linked glucose-6-phosphate dehydrogenase (G6PD) deficiency has been recovered in offspring of 1-ethyl-1-nitrosourea-treated male mice. The activity alteration was detected in blood but can also be observed in other tissue extracts. Hemizygous, heterozygous, and homozygous mutants have, respectively, about 15, 60, and 15% G6PD remaining activity in the blood as compared to the wild type. Erythrocyte indices did not show differences between mutants and wild types. The mutation does not affect the electrophoretic migration, the isoelectric point, or the thermal stability. Kinetic properties, such as theK_m for glucose-6-phosphate or for NADP and the relative utilization of substrate analogues, showed no differences between wild types and mutants with the exception of the relative utilization of deamino-NADP which was significantly lower in mutants. This is presently the only animal model for X-linked G6PD deficiency in humans.This research was supported in part by Contract BI6-156-D from the Commission of the European Communities.     

Stability of DNA-protein interactions in chromatin fractions with different sensitivity to nucleases

It was revealed by means of nucleoprotein-celite-chromatography that DNA-protein interactions in the chromatin fraction sensitive to micrococcal nuclease and DNase II are weaker that in the resistant one. The micrococcal nuclease destroys the DNA-matrix bond resistant to salt-urea, while DNase II does not change the DNA-matrix integrity. Tightness of the DNA-protein interactions is weakened by the increasing chromatin fragmentation, but does not depend on the size of chromatin particles.     

Biochemical characterization of chromatin fractions isolated from induced and uninduced friend erythroleukemia cells

Summary Chromatin fractions from Friend erythroleukemia cells after induction of differentiation by dimethylsulfoxide (DMSO) were compared in their biochemical characteristics to fractions from uninduced cells. Fractions were prepared by extracting chromatin from nuclei after mild micrococcal nuclease treatment with increasing concentrations of NaCl according to Sanders [1]. This procedure has been found to release chromatin containing hyperacetylated histones preferentially [2]. The fractions obtained by this procedure were analysed in respect to the amount of chromatin released, the amount of histone H1, the degree of acetylation of histone H4, the presence of non-histone proteins and the concentration of transcribed and non-transcribed sequences. It was found that the fractions differ in the amount of histone H1 present, in several non-histone proteins and in the acetylation of histonie H4, regardless whether induced or uninduced cells were analysed. The distribution of transcribed sequences versus non-transcribed sequences among the fractions was the same, demonstrating that this fractionation procedure, although leading to fractions with biochemical differences, is not able to discriminate functional states of chromatin and that the biochemical characteristics of the fractions may be common to both, active as well as inactive states of chromatin.     

Distribution of estradiol receptor and vitellogenin gene in chick liver chromatin fractions.

The distribution of estradiol receptor and vitellogenin gene was studied in estradiol stimulated chick liver chromatin fractions prepared by limited DNAse II digestion and MgCl2 precipitation. The receptor was found in all fractions, undigested chromatin (P1), Mg2+ insoluble chromatin (P2) and Mg2+ soluble chromatin (S2). This last fraction was rich in acidic proteins, had a high protein:DNA ratio (7.0 w/w), contained 28% of rapidly labelled RNA, 20% of the receptor, 3-5% of chromatin DNA and showed a 2 fold enrichment of vitellogenin DNA sequences over unfractionated chromatin as well as P1 and P2 DNA. On isopycnic metrizamide gradients, all chromatin fractions showed a receptor peak banding at 1.23 g/cm3, the density of nucleoproteins. Hybridization experiments showed that the DNA banding at this density in fraction S2 was enriched 4 fold in vitellogenin DNA sequences over unfractionated chromatin as well as P1 and P2 DNA. These results suggest an association of hormone receptor complex with nucleoprotein structures of an apparently active chromatin fraction.     

Characterization of two major non-histone protein fractions from chromatin of sea urchin embryos

• 1.1. Chromatin of sea urchin embryos was chromatographed on a hydroxyapatite column, and the two largest fractions of proteins desorbed with 0.05 M and 0.2 M Na-phosphate, pH 6.8, were comparatively characterized.
• 2.2. The mol. wt ranges of these fractions were about 18,000 and 14,000 daltons, respectively, at both molarities of the phosphate buffer.
• 3.3. Both fractions at each elution molarity were found to be acidic, and to differ somewhat in their respective amino acid compositions. No important differences related to the stage of development could be detected in this respect.
• 4.4. Upon re-electrophoresis both large fractions resolved in one major and three minor bands. The amino acid composition of the major band was different for the blastula and gastrula chromatin.
• 5.5. It is likely that these fractions contain glycoprotein subunits.