Topological Complexity of SV40 Minichromosomes

During attempts to measure the extent to which the proteins of simian virus 40 (SV40) minichromosomes restrain the ability of SV40 DNA to alter its twist in response to temperature changes, we found that temperature- shift-induced linking number changes are not reversible for isolated minichromosome...

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Bibliographic Details
Published in:Journal of molecular biology 1996-03, Vol.257 (1), p.53-65
Main Authors: Givens, Robert M., Saavedra, Raul A., Huberman, Joel A.
Format: Article
Language:English
Subjects:
DNA flexibility
DNA Replication
DNA topoisomerase
DNA topology
DNA, Viral - chemistry
DNA, Viral - genetics
Molecular Structure
simian virus 40
Simian virus 40 - genetics
Temperature
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Summary:During attempts to measure the extent to which the proteins of simian virus 40 (SV40) minichromosomes restrain the ability of SV40 DNA to alter its twist in response to temperature changes, we found that temperature- shift-induced linking number changes are not reversible for isolated minichromosomes, suggesting that such changes, both in isolated minichromosomes and in cells, may be a consequence of structural alterations in chromatin proteins rather than of simple changes in DNA twist. We also found that the SV40 minichromosome pool is composed of subpopulations that display different responses to temperature shifts. For example, the linking number of DNA in newly replicated minichromo somes is more responsive to in vivotemperature changes than is the linking number of DNA in bulk minichromosomes. In addition, the linking number profiles of both isolated and intracellular minichromosomes change during the course of infection. These observations emphasize the topological complexity of SV40 minichromosomes and encourage caution in the interpretation of experiments carried out on bulk minichromosomes.
ISSN:0022-2836
1089-8638
DOI:10.1006/jmbi.1996.0146