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Attachment to the nuclear matrix mediates specific alterations in chromatin structure
A Pemov1, S Bavykin, J L Hamlin
1Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
Summary
Nuclear matrix attachment dramatically alters chromatin structure at replication origins during the cell cycle. This change, however, does not affect gene promoter regions, suggesting a role in origin activation.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Eukaryotic DNA is organized into loops attached to the nuclear matrix at specific regions.
- The impact of nuclear matrix attachment on chromatin architecture in regulatory regions like replication origins and gene promoters remains unclear.
Purpose of the Study:
- To investigate cell-cycle-dependent chromatin structure changes in replication initiation zones.
- To determine the effect of nuclear matrix attachment on chromatin architecture in these regions.
Main Methods:
- Studied the amplified dihydrofolate reductase domain in methotrexate-resistant Chinese hamster ovary cells (CHOC 400).
- Analyzed chromatin structure using micrococcal nuclease hypersensitivity assays.
- Examined cell-cycle-dependent changes across the G1/S boundary.
Main Results:
- Significant alterations in chromatin micrococcal nuclease hypersensitivity were observed in ori-beta and ori-gamma regions upon cell cycle progression (G1/S boundary).
- These chromatin changes occurred specifically in DNA copies attached to the nuclear matrix.
- No detectable changes in chromatin structure were found in the dihydrofolate reductase gene promoter, irrespective of matrix attachment or cell cycle stage.
Conclusions:
- Attachment to the nuclear matrix plays a crucial role in modulating chromatin architecture.
- These matrix-associated chromatin modifications may facilitate the activity of replication origins.