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Nick-forming sequences may be involved in the organization of eukaryotic chromatin into ∼50 kbp loops

Lookup NU author(s): Professor Caroline Austin

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Abstract

Phenomena involving the disassembly of chromosomes to ∼50 kbp double-stranded fragments upon protein denaturing treatments of normal and apoptotic mammalian nuclei as well as yeast protoplasts may be an indication of special, hypersensitive regions positioned regularly at loop-size intervals in the eukaryotic chromatin. Here we show evidence in yeast cell systems that loop-size fragmentation can occur in any phase of the cell cycle and that the plating efficiency of these cells is ∼100%. The possibility of sequence specificity was investigated within the breakpoint cluster region (bcr) of the human MLL gene, frequently rearranged in certain leukemias. Our data suggest that DNA isolated from yeast cultures or mammalian cell lines carry nicks or secondary structures predisposing DNA for a specific nicking activity, at non-random positions. Furthermore, exposure of MLL bcr-carrying plasmid DNA to S1 nuclease or nuclear extracts or purified topoisomerase II elicited cleavages at the nucleotide positions of nick formation on human genomic DNA. These data support the possibility that certain sequence elements are preferentially involved in the cleavage processes responsible for the en masse disassembly of chromatin to loop-size fragments upon isolation of DNA from live eukaryotic cells. © Springer-Verlag 2005.


Publication metadata

Author(s): Szekvolgyi L, Hegedus E, Molnar M, Bacso Z, Szarka K, Beck Z, Dombradi V, Austin C, Szabo G

Publication type: Article

Publication status: Published

Journal: Histochemistry and Cell Biology

Year: 2006

Volume: 125

Issue: 1-2

Pages: 63-73

ISSN (print): 0948-6143

ISSN (electronic): 1432-119X

Publisher: Springer

URL: http://dx.doi.org/10.1007/s00418-005-0073-1

DOI: 10.1007/s00418-005-0073-1

PubMed id: 16195888


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