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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In vitro studies have demonstrated that the estrogen receptor (ER) can bind to the rat PRL estrogen response element (ERE) located 1700 basepairs upstream of the transcriptional start site. However, the mechanism by which the receptor-DNA complex influences the activity of RNA polymerase located in the promoter region is not understood. To begin investigating this process, we developed cell lines derived from GH3 cells that contain steroid-responsive bovine papillomavirus minichromosomes. Within these minichromosomes is a hybrid gene composed of the 5' flanking region of the PRL gene, driving the expression of the Tn5 gene. The episomal PRL DNA sequences responded to 17 beta-estradiol (E2) by increasing the rate of Tn5 gene transcription. Nucleosome mapping experiments using micrococcal nuclease demonstrated that nucleosome-like structures were assembled on the minichromosome in an ordered array separated by 150-200 basepairs of DNA. Novel S1 nuclease as well as DNase-I-hypersensitive sites in the chromatin of the promoter and distal regulatory regions of the episomal PRL gene were detected by indirect end-labeling studies. The nuclease hypersensitive sites in the distal region containing the ERE were modified after treatment of the cells with either E2 or the antiestrogen 4-hydroxytamoxifen. However, only E2 treatment of cells resulted in an increase in the nuclease hypersensitivity of the promoter region and induced gene expression, while antiestrogen treatment had no effect on either parameter. This suggests that complex interactions between factors located at the distal and proximal regulatory regions ultimately determine the transcriptional response of the PRL gene to E2.
Mol Endocrinol 1990 Aug
PMID:An interaction between the 5' flanking distal and proximal regulatory domains of the rat prolactin gene is required for transcriptional activation by estrogens. 196 74

Circular plasmid DNA molecules and linear concatemers formed from the same plasmid exhibit strikingly different fates following microinjection into Xenopus laevis embryos. In this report, we prove quantitatively that only a minority of small, circular DNA molecules were replicated (mean = 14%) from fertilization through the blastula stage of development. At all concentrations tested, very few molecules (approximately 1%) underwent more than one round of DNA synthesis within these multiple cell cycles. In addition, unlike endogenous chromatin, the majority of circular templates became resistant to cleavage by micrococcal nuclease. The extent of nuclease resistance was similar for both replicated and unreplicated templates. Sequestration of circular molecules within a membranous compartment (pseudonucleus), rather than the formation of nucleosomes with abnormal size or spacing, apparently conferred the nuclease resistance. In contrast, most linearly concatenated DNA molecules (derived from end-to-end joining of microinjected monomeric plasmid DNA) underwent at least two rounds of DNA replication during this same period. Linear concatemers also exhibited micrococcal nuclease digestion patterns similar to those seen for endogenous chromatin yet, as judged by their failure to persist in later stages of embryogenesis, were likely to be replicated and maintained extrachromosomally. We propose, therefore, that template size and conformation determine the efficiency of replication of microinjected plasmid DNA by directing DNA to a particular compartment within the cell following injection. Template-dependent compartmentalization may result from differential localization within endogenous nuclei versus extranuclear compartments or from supramolecular assembly processes that depend on template configuration (e.g., association with nuclear matrix or nuclear envelope).
Mol Cell Biol 1991 Jan
PMID:Differential compartmentalization of plasmid DNA microinjected into Xenopus laevis embryos relates to replication efficiency. 198 27

The expression of the gene coding for chromosomal protein HMG-17 is down regulated during chicken erythrocyte maturation. The transcriptional down regulation is associated with major alterations in the chromatin structure of this gene. The 5' region of the gene contains both constitutive and developmental stage-specific deoxyribonuclease I (DNase I) hypersensitive sites. The constitutive sites bracket the "CpG island" present in the gene, which remains hypomethylated throughout the various developmental stages. During erythropoiesis, the gene acquires a distinct structure that, upon digestion with micrococcal nuclease (MNase) yields an unusual repeat. Two nucleosomes, with a 200 base-pair repeat, are positioned immediately downstream from the start of transcription. Immediately downstream and upstream from these nucleosomes, the boundaries between MNase sites change to a 75 base-pair repeat, which indicates an unusual chromatin structure. The differentiation related changes in the DNase I and MNase digestion pattern in the 5' region of the gene suggest that sequences present in the first intron may be involved in gene regulation. The results may be relevant to the regulation of the entire HMG-14/-17 gene family.
J Mol Biol 1991 Jan 05
PMID:Differentiation-dependent alteration in the chromatin structure of chromosomal protein HMG-17 gene during erythropoiesis. 198 81

The preparation of hybrid histone octamers with wheat histone H2A variants replacing chicken H2A in the chicken octamer is described. The fidelity of the reconstituted hybrid octamers was confirmed by dimethyl suberimidate cross-linking. Polyglutamic-acid-mediated assembly of these octamers on long DNA and subsequent micrococcal nuclease (MNase) digestion demonstrated that, whereas chicken octamers protected 167 base-pairs (representing 2 full turns of DNA), hybrid histone octamers containing wheat histone H2A(1) with its 19 amino acid residue C-terminal extension protected an additional 16 base pairs of DNA against nuclease digestion. The protection observed by hybrid histone octamers containing wheat histone H2A(3) with both a 15 residue N-terminal and a 19 residue C-terminal extension was identical with that observed with H2A(1)-containing hybrid histone octamers with only the 19 residue C-terminal extension. These results suggest that the role of the C-terminal extension is to bind to DNA of the "linker" region. The thermal denaturation of chicken and hybrid core particles was identical in 10 mM-Tris.HCl.20 mM-NaCl, 0.1 mM-EDTA, confirming that there was no interaction between the basic C-terminal extension and DNA of the core particle. Denaturation in EDTA, however, showed that hybrid core particles had enhanced stability, suggesting that the known conformational change of core particles at very low ionic strength allows the C-terminal extension to bind to core particle DNA under these conditions. A model accounting for the observed MNase protection is presented.
J Mol Biol 1991 Apr 20
PMID:Extended C-terminal tail of wheat histone H2A interacts with DNA of the "linker" region. 202 50

The chromatin structure of Entamoeba histolytica was investigated. It was found that this protozoan organizes its chromatin in nucleosome-like particles 10 nm in diameter, but digestion of the chromatin with micrococcal nuclease did not render a regularly spaced DNA ladder in agarose gels. Southern blot analysis of the products of Entamoeba chromatin digestion using total amebic DNA and a non-transcribed repetitive sequence produced a banding pattern characteristic of eukaryotic chromatin with a repetitive size of approximately 130 bp. Conversely, hybridization with two active gene probes, actin and ribosomal RNA, showed that these sequences are not part of the chromatin organized in nucleosomes. It was also found that the basic nuclear proteins differ from histones of higher eukaryotes in electrophoretic mobility. Screening of an E. histolytica HM1-IMSS genomic library with Saccharomyces cerevisiae H3 and H4 genes and attempts to amplify E. histolytica sequences, homologous to these yeast histone genes, gave negative results suggesting that the Entamoeba proteins involved in chromatin organization are not typical histones.
Mol Biochem Parasitol 1991 Mar
PMID:Chromatin organization in Entamoeba histolytica. 205 32

We report on a dynamic aspect of nucleosome positioning, in the absence of transcription-related events, on sea urchin 5 S rDNA. On tandem repeats of nucleosome length DNA of this strongly positioning sequence, histone octamers assemble in one dominant position surrounded by minor positions, ten base-pairs apart and therefore with identical rotational setting of the DNA coil. The existence of this cluster of positions, determined using micrococcal nuclease is confirmed by the results from DNase I footprinting and restriction enzyme analysis. The results from these techniques and from two-dimensional nucleoprotein polyacrylamide gel analysis indicate that the cluster of octamer positions is in dynamic equilibrium, in low ionic conditions, suggesting that the minor positions reflect fluctuations around the major nucleosome site. Histone octamer mobility appears to be temperature dependent and is reversibly inhibited by Mg2+.
J Mol Biol 1991 Jul 05
PMID:Mobility of positioned nucleosomes on 5 S rDNA. 206 9

The nucleosomal aggregates were obtained by micrococcal nuclease treatment to chicken erythrocyte nuclei. There still leaves a bulk of nucleosomes. We used two different DNA assay methods to determine DNA in in situ nucleosomes; the Feulgen DNA assay which shows a positive apurinic acid, and the fluorometry with Hoechst 33258 which reveals only intact AT base pairs. On applying those methods to the aggregates, even in a short digestion, Feulgen DNA remains only about 1/4 of the non-digested nuclei and the fluoroassay leaves only a trace amount of AT base pairs. Thus, the nucleosomes derived from the heterochromatin of erythrocytes are not preserved as the residual DNA of Feulgen hydrolysis. This also suggests that the bulk of nucleosomal DNA is masked and sensitive to neither the Feulgen assay nor the fluorometry of AT base pairs.
Cell Mol Biol 1990
PMID:Deduction of DNA from artificial aggregates of erythrocyte nucleosomes. 207 81

Light micrococcal nuclease digestion was used to examine DNA associated with nucleosome populations isolated from Alzheimer's disease (AD) affected superior temporal lobe neocortical nuclei. 46.1% of the immediate 5' upstream DNA sequence of the single copy neurofilament light chain (NF-L) gene was found to be associated with a mononucleosome fraction in control neocortices. This fraction was reduced to 7.4% in age-matched AD-affected neocortex. No differences in accessibility to the nuclease probe was found between AD-affected and control temporal grey matter nuclei for the human prion HuPrP gene or for the NF-L gene in nuclei isolated from the primary visual cortex or the cerebellum. An AvaI restriction endonuclease site, located 124 base pairs upstream from the TATAA box in the NF-L leader sequence, was also found to be occluded in AD-affected nuclei. From this and previous data we conclude that within the AD-affected nucleus, focused changes in neuronal chromatin conformation occur. Increases in the packing density of chromatin may reduce transcription and alter the ability of neurons to generate sufficient levels of gene products to maintain normal neocortical function.
Brain Res Mol Brain Res 1990 Apr
PMID:Chromatin structure and gene expression in Alzheimer's disease. 215 82

Over the past decade, the results of numerous indirect mappings analyses have not clarified whether or not nucleosomes occupy preferred positions in simian virus 40 (SV40) chromatin. To address this question more directly, we followed a shotgun cloning approach and determined the nucleotide sequences of over 400 cloned nucleosomal DNA fragments obtained from digestion of SV40 chromatin with micrococcal nuclease. Our results demonstrate and establish that nucleosomes do not occupy unique positions in SV40 minichromosomes and thus indicate the existence of at least several types of chromatin molecules having different nucleosome organization patterns. We developed two types of statistical analysis in order to examine the cloning data in greater detail. One type, overlap analysis, revealed the distribution of the cloned fragments with respect to SV40 DNA. The distribution exhibits an oscillating pattern, dividing the genome into regions of weak or strong nucleosome density. The other analysis determined the distribution of the midpoints of the cloned fragments and revealed potential strong and weak nucleosome location sites, and an early versus late distinction in organization of nucleosomes in SV40 chromatin. The late region appears to contain more strong nucleosome location sites (8) than the early region (4). The strongest nucleosome abuts the late side of the nuclease-hypersensitive region and includes the major transcription initiation site of the late genes. Another strong site precedes this nucleosome and includes sequences implicated in controlling the expression of the SV40 early and late genes. A strong or weak nucleosome location site is not apparent near the early side of the nucleosome-hypersensitive region. Only weak and overlapping nucleosome location sites are found in the region where replication terminates in the SV40 minichromosomes.
J Mol Biol 1990 Aug 20
PMID:Location of nucleosomes in simian virus 40 chromatin. 216 81

We have compared the mononucleosomal pattern produced by micrococcal nuclease digestion of condensed and unfolded chromatin and chromatin in nuclei from various sources with the repeat length varying from 165 to 240 base-pairs (bp). Upon digestion of isolated H1-containing chromatin of every tested type in a low ionic strength solution (unfolded chromatin), a standard series of mononucleosomes (MN) was formed: the core particle, MN145, and H1-containing, MN165, MN175, MN185, MN195, MN205 and MN215 (the indexes give an approximate length of the nucleosomal DNA that differs in these particles by an integral number of 10 bp). In addition to the pattern of unfolded chromatin, digestion of whole nuclei or condensed chromatin (high ionic strength of Ca2+) gave rise to nuclei-specific, H1-lacking MN155. Digestion of H1-lacking chromatin produced only MN145, MN155 and MN165 particles, indicating that the histone octamer can organize up to 165 bp of nucleosomal DNA. Although digestion of isolated sea urchin sperm chromatin (repeat length of about 240 bp) at a low ionic strength gave a typical "unfolded chromatin pattern", digests of spermal nuclei contained primarily MN145, MN155, MN235 and MN245 particles. A linear arrangement of histones along DNA (primary organization) of the core particle was found to be preserved in the mononucleosomes, with the spacer DNA length from 10 to 90 bp on one (in MN155) or both sides of core DNA being a multiple of about 10 bp. In MN235, the core particle occupies preferentially a central position with the length of the spacer DNA on both sides of the core DNA being usually about 30 + 60 or 40 + 50 bp. Histone H1 is localized at the ends of these particles, i.e. close to the centre of the spacer DNA. The finding that globular part of histones H3 and sea urchin sperm H2B can covalently bind to spacer DNA suggests their involvement in the organization of chromatin superstructure. Our data indicate that decondensation of chromatin is accompanied by rearrangement of histone H1 on the spacer DNA sites adjacent to the core particle and thus support a solenoid model for the chromatin superstructure in nuclei in which the core DNA together with the spacer DNA form a continuous superhelix.
J Mol Biol 1990 Apr 05
PMID:Structure of nucleosomes and organization of internucleosomal DNA in chromatin. 232 31


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