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Query: EC:3.1.31.1 (micrococcal nuclease)
 2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Extracts prepared from Friend erythroleukemia cells were highly active in translating endogenous mRNA and a consistent 2-fold stimulation by hemin was observed. When extracts were treated with micrococcal nuclease and incorporation was dependent on exogenous globin mRNA, there was more significant stimulation by 37.5 micron hemin and greater than 10-fold stimulation by 75 or 150 micron hemin. The effects of hemin were not strikingly different in extracts of dimethyl-sulfoxide-induced or uninduced cells. The results could reflect an effect on initiation of protein synthesis analogous to that in rabbit reticulocytes.
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PMID:Stimulation of protein synthesis by hemin in extracts of Friend erythroleukemia cells. 27 42

The protein IP25, which has previously been reported to accumulate in the chromatin during erythroid differentiation of Friend-virus-transformed erythroleukemia cells (FL cells), is shown to behave like histone H1 without being structurally related to it. Like H1, IP25 is not released by digestion of FL cells nuclei with DNAse I. After micrococcal digestion IP25 and H1 are differentially distributed in the nucleosome monomers and dimers. This distribution suggests an internucleosomal location for IP25 and H1. Different rates of digestion are observed between nuclei of differentiating and non-differentiating FL cells with both DNAse I and micrococcal nuclease. These differences could be due to the presence of IP25 in the chromatin of differentiating cells.
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PMID:Biochemical properties and localization of the chromosomal protein IP25. 28 82

A message-dependent, cell-free translation system was prepared from both uninduced and N,N'-hexamethylene-bis-acetamide-induced Friend erythroleukemia cells following modification of standard protocols. Active extracts were prepared by lysing Friend erythroleukemia cells in hypotonic buffer containing 50 microM hemin and 10 mM cyclic adenosine monophosphate (cAMP), and assaying translation in vitro in the absence of exogenous nucleoside triphosphates. Both hemin and cAMP were required for full activity and appeared to act by prolonging initiation in vitro. Following treatment of cell extracts with micrococcal nuclease, brome mosaic virus, globin, equine herpesvirus type 1, and frog virus 3 mRNA were efficiently translated to yield full-sized products. Using brome mosaic virus as a test message, levels of translation equivalent to 30%-50% of that seen in mock-treated lysates were obtained. These results attest to the translational efficiency of extracts prepared and assayed in the manner described above, and suggest that such extracts may be useful both for routine translational studies, and as a tool to dissect translational changes accompanying erythroid differentiation in vitro.
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PMID:Hemin and cyclic AMP stimulate message-dependent translation in lysates from Friend erythroleukemia cells. 254 Oct 8

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. This procedure has been found to release chromatin containing hyperacetylated histones preferentially. 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 histone 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.
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PMID:Biochemical characterization of chromatin fractions isolated from induced and uninduced Friend erythroleukemia cells. 257 Oct 75

We used micrococcal nuclease to separate murine erythroleukemia cell (MELC) chromatin into soluble and insoluble fractions which differ in gene content and chromatin structure. Genes that are not expressed in the erythroid lineage, such as the Ig alpha and albumin genes, distribute preferentially into the soluble rather than the insoluble fraction, and are organized into nucleosomes in both fractions. Both alpha 1- and beta maj-globin genes are enriched in the insoluble fraction and are organized into structures that are partially devoid of nucleosomes in uninduced MELC, when the genes are transcriptionally inactive. Following chemical induction of MELC and the onset of globin gene transcription, globin gene enrichment and nucleosome disruption in the insoluble chromatin fraction increase. Using seven DNA subclones that span the beta maj-globin gene we show that insolubility and nucleosome disruption are largely limited to DNA sequences lying within the transcribed domain. Non-transcribed, flanking sequences are soluble and organized into nucleosomes. In addition, the globin genes found in insoluble, non-nucleosomal chromatin contain previously engaged RNA polymerases which can elongate globin RNA chains in vitro in a pattern qualitatively and quantitatively similar to intact nuclei. These results are discussed in terms of a model for globin gene activation during erythropoeisis.
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PMID:Nucleosome disruption precedes transcription and is largely limited to the transcribed domain of globin genes in murine erythroleukemia cells. 258 37

The turnover rates of some mRNAs vary by an order of magnitude or more when cells change their growth pattern or differentiate. To identify regulatory factors that might be responsible for this variability, we investigated how cytosolic fractions affect mRNA decay in an in vitro system. A 130,000 X g supernatant (S130) from the cytosol of exponentially growing erythroleukemia cells contains a destabilizer that accelerates the decay of polysome-bound c-myc mRNA by eightfold or more compared with reactions lacking S130. The destabilizer is deficient in or absent from the S130 of cycloheximide-treated cells, indicating that it is labile or is repressed when translation is blocked. It is not a generic RNase, because it does not affect the turnover of delta-globin, gamma-globin, or histone mRNA and does not destabilize a major portion of polysomal polyadenylated mRNA. The destabilizer accelerates the turnover of the c-myc mRNA 3' region, as well as subsequent 3'-to-5' degradation of the mRNA body. It is inactivated in vitro by mild heating and by micrococcal nuclease, suggesting that it contains a nucleic acid component. c-myb mRNA is also destabilized in S130-supplemented in vitro reactions. These results imply that the stability of some mRNAs is regulated by cytosolic factors that are not associated with polysomes.
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PMID:Regulation of c-myc mRNA stability in vitro by a labile destabilizer with an essential nucleic acid component. 274 42

DNA of mouse erythroleukemia cells grown in vitro was labeled with bromodeoxyuridine during cycloheximide-inhibited protein synthesis. Isolated nuclei were digested with micrococcal nuclease to obtain monosomes and monosomal dsDNA. The protection of the heavy and of the light strands of the newly replicated DNA was studied by dot hybridization with the coding and with its complementary noncoding strand of the alpha-globin gene. The results show that both sides of the replication fork contain protected sequences of the gene, thus supporting a bilateral (dispersive) mode of nucleosome segregation during DNA replication.
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PMID:Segregation of nucleosomes in replicated mouse alpha-globin gene. 303 89

During differentiation of murine erythroleukemia cells, adult beta-globin gene chromatin acquires site-specific, DNase I hypersensitivity and an increased sensitivity in the globin gene region toward micrococcal nuclease (MNase) digestion. The relationship of these changes in chromatin structure to globin gene activation and to cellular commitment events has been studied. Imidazole, which blocks globin gene transcription during induction does not affect the terminal differentiation of the cells nor does it prevent the acquisition of DNAse I hypersensitivity. The formation of the inducible DNase I-hypersensitive site near the globin gene accompanies the developmental events which lead to cellular differentiation independent of the transcription process. The increased MNase sensitivity of the adult beta-globin gene region, normally preceded by the acquisition of 5' DNase I hypersensitivity, was blocked by the addition of imidazole prior to but not after globin gene activation. The enhanced MNase sensitivity was not abolished by the addition of actinomycin D and, thus, reflects a part of chromatin alterations that define potential for transcription. Therefore, there is a sequential series of chromatin alterations in the globin gene region associated with murine erythroleukemia cell differentiation. The appearance of the inducible 5' DNase I-hypersensitive site precedes the onset of globin gene transcription and is strongly correlated with commitment events. The enhanced MNase sensitivity is closely related to globin gene transcription, but it is not a consequence of the transcription process. In addition, the commitment of cells to terminal differentiation is dissociable from the stimulation of globin gene transcription.
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PMID:Sequential alterations in globin gene chromatin structure during erythroleukemia cell differentiation. 385 50

Adult beta-globin gene chromatin in murine erythroleukemia (MEL) cells acquired increased sensitivity to both micrococcal nuclease and DNase I during hexamethylenebisacetamide-induced erythoid differentiation. The DNase I hypersensitivity of the globin genes accompanied their actual transcription and was strongly correlated with commitment events. On the other hand, the rate of micrococcal nuclease digestion was closely related to the rate of globin gene transcription. Two distinct DNase I hypersensitive sites were found on the 5' side of the beta-major globin gene in HMBA-induced cells. One site was located near the 5' side of the beta-major globin gene and the second site was located approximately 3 kilobases upstream of the beta-major cap site. Following the commitment of MEL cells to differentiate, DNase I sensitivity was stably inherited in the absence of inducer. In contrast to HMBA, another inducer, hemin, known to cause the accumulation of globin-specific mRNA in MEL cells by a post-transcriptional mechanism, did not elicit alterations of beta-globin gene chromatin. The addition of dexamethasone, a hormone known to inhibit MEL cell commitment, blocked the formation of general and site-specific nuclease sensitivity of beta-globin gene chromatin prior to but not after cell commitment.
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PMID:Alterations in globin gene chromatin conformation during murine erythroleukemia cell differentiation. 623 Dec 95

We have analyzed the chromatin structure of the beta-major globin gene and other related beta-globin genes in induced and uninduced murine erythroleukemia (MEL) cell nuclei. Nuclei were digested with either DNase I or micrococcal nuclease, and the purified DNA was hybridized to a set of cloned genomic DNA fragments covering the beta-globin gene region. This region consisted of two distinct domains as characterized by sensitivity to DNase I digestion. One domain was relatively sensitive and contained the potentially active or actively transcribed beta-major and beta-minor globin genes. The other, relatively insensitive domain contained the nontranscribed embryonic and beta-globin homologous genes. The sensitivity of these domains was not altered during erythroid differentiation. In nonerythroid cells, the entire globin gene family, including the adult and embryonic globin genes, was contained in a single relatively resistant domain. Micrococcal nuclease (MNase) also defined two general domains of nuclease sensitivity that coincided with those of DNase I. However, the relatively sensitive MNase domain containing the beta-major and beta-minor genes became more sensitive upon chemically stimulated erythroid differentiation. A detailed examination of the beta-major globin gene revealed that the actual coding region became increasingly sensitive to micrococcal nuclease after differentiation while the 5'-flanking DNA did not. Thus, micrococcal nuclease was able to accurately define the primary transcription unit of the beta-major gene.
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PMID:Chromatin structure of the beta-globin gene family in murine erythroleukemia cells. 623 52


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