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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)

The structure of the chicken adult beta-globin gene chromatin in immature and mature erythrocyte nuclei has been analysed using micrococcal nuclease digestion. The resulting DNA fragments were blotted onto DBM-papers and probed with labelled DNA fragments spanning the adult beta-globin gene and its 5'- and 3'-flanking regions. The structure of the nucleosomes within and in the regions flanking the adult beta-globin gene appears to be altered in at least two ways in erythrocyte chromatin, when compared with either bulk or inactive ovalbumin gene chromatin. First, oligomeric DNA fragments containing the beta-globin gene are released faster than those of either bulk or ovalbumin gene chromatin. Second, although the difference in size of the liberated oligomeric DNA fragments is similar to the nucleosomal repeat length of bulk and ovalbumin gene chromatin, the individual oligomers are approximately 100 bp shorter than their bulk or ovalbumin gene counterparts, most noticeably when the nuclease digestion is performed at 37 degrees C. This results in an atypical ladder of approximately 300, 500, 700, 900 bp instead of the canonical chicken erythrocyte ladder which is an integral multiple of 207 bp. The same ladder was obtained from immature erythrocytes, in which the beta-globin gene is actively transcribed, and from mature erythrocytes, in which it is considered to be inactive with RNA polymerase molecules clustered in the 5' moiety of the gene. This indicates that the alteration of the nucleosomal structure is not due to transcription per se.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Digestion of the chicken beta-globin gene chromatin with micrococcal nuclease reveals the presence of an altered nucleosomal array characterized by an atypical ladder of DNA fragments. 301

Chromatin structure of ribosomal genes from nuclei of Drosophila melanogaster embryos was studied by using micrococcal nuclease cleavage. End-directed labelling with short cloned fragments of the ribosomal repeat was carried out. It shows, that the micrococcal nuclease prefers specific sites in naked DNA, and the pattern of DNA cleavage is essentially conserved when the nuclei are digested. Only minor differences are visible. Hence, there are no specific positions of nucleosomes on the ribosomal repeat. The DNA fragments from the nuclei treated with micrococcal nuclease were electrophoresed, transferred to DBM-paper and hybridized with different probes subcloned from the ribosomal repeat. The non-transcribed spacer and the region of the beginning of transcription are hydrolysed significantly faster than the coding region or inactive ribosomal insertion. The region of NTS and the beginning of transcription do not give normal nucleosomal fragment in the range of 145-185 bp; instead they produce a heterogeneous band 200-280 bp in length even after prolonged digestion. Dinucleosomal fragments are also slightly longer and more heterogeneous than in other parts of the ribosomal repeat. Higher oligomers are similar throughout the ribosomal repeat. We suggest that a hypothetical transcription factor interacts in a way with histones and protects unusual fragments of DNA from digestion.
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PMID:[Chromatin structure of ribosomal genes of Drosophila melanogaster. Random location of nucleosomes in DNA and characteristics of organization of non-transcribed spacer]. 609 27

The precise chromatin structure of actively transcribed DNA in yeast has been analyzed by electrophoretic transfer of high-resolution staphylococcal nuclease and DNase I chromatin digest DNA patterns to DBM paper and hybridization with active sequence probes. The DNA patterns of the transcribed DNA sequences resemble the DNA patterns produced by digestion of bulk yeast nucleosomes. Hence, these active sequences must be arranged in "typical" nucleosome structures. Furthermore, in details of the structure, the active sequence nucleosomes look almost exactly like the average yeast nucleosome in repeat length, in the length of DNA associated with the core particle, in the amount and type of heterogeneity found within and between the oligomeric and monomeric repeat lengths of DNA, in the occurrence of discrete spacer lengths including the characteristic five nucleotide increments (i.e., 5, 15, 25, ... base pairs), and in the length of DNA between yeast nucleosomes. Early in digestion, there are some differences: increases in peak breadths (i.e., in the distribution of spacer lengths) and some preferential release of monomer DNA. These results suggest that transcribed DNA can exist in the typical (yeast) type of nucleosome organization and thus that active chromatin regions do not necessarily require profound structural rearrangements. The slight differences noted are consistent with some slight, mainly spacer, modification in the vicinity of the transcription event itself.
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PMID:Detailed analysis of the nucleosomal organization of transcribed DNA in yeast chromatin. 627 32

The ribosomal genes of Dictyostelium discoideum are extrachromosomal palindromic DNA molecules situated in the nucleolus. Each molecule comprises ribosomal RNA coding regions and non-transcribed spacer regions. We used both biochemical and electron microscopic approaches to investigate the structure of transcribing and non-transcribing chromatin. Nucleoli from exponentially growing cells were digested with micrococcal nuclease, and the resulting DNA fragments were separated by gel electrophoresis and transferred to DBM paper. They were hybridized with cloned EcoRI fragments derived from different parts of the ribosomal gene. Probes of the coding region showed a smear, while probes of the non-transcribed regions gave pronounced banding patterns more complex than typical nucleosome repeats, but not due solely to sequence-specific cutting by micrococcal nuclease. The DNA of the coding region was digested more quickly than that of the non-transcribed ones. When nucleoli were digested with restriction enzymes, sites within the coding region were accessible and sites in the non-transcribed region were protected. The structure of ribosomal chromatin in differentiating cells, in which the rate of ribosomal RNA synthesis is reduced, was examined using essentially the same methods. The coding region, probed by hybridization to micrococcal digests, then showed a typical DNA repeat pattern indicating that this region had become condensed into nucleosomes, and its accessibility to restriction enzymes was very much reduced. On electron micrographs of lysed nucleoli from exponentially growing cells, two types of chromatin were observed, one with a beaded nucleosomal appearance, the other with putative RNA polymerase molecules attached to fibres indistinguishable from free DNA adsorbed to the same grid. The combined results suggest that whereas regions that are not transcribed are packaged with proteins that protect them from nuclease digestion, actively transcribing ribosomal genes are associated with few macromolecular constituents apart from those required for transcription and its regulation.
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PMID:Chromatin structure along the ribosomal DNA of Dictyostelium. Regional differences and changes accompanying cell differentiation. 630 25

Relative abundance of nucleosomes on reconstituted chromatin was estimated with cloned mouse beta-globin gene DNA. Mononucleosomal DNA was isolated from reconstituted chromatin after digestion with micrococcal nuclease, nick-translated and used as a probe for blot hybridization. DNA fragments of restriction nuclease-digested globin DNA were transferred to DBM-paper and hybridized with mononucleosomal [32P] DNA probe. The results showed non-random distribution of nucleosomes.
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PMID:Distribution of nucleosomes on reconstituted chromatin from cloned mouse beta-globin DNA. 687 97