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Comparison of nuclease digestion of polyoma virus nucleoprotein complex and mouse chromatin
Abstract:
We digested polyoma virus nucleoprotein complex, isolated from disrupted virions, with micrococcal nuclease and DNase I. The results were compared with digestions of chromatin from mouse nuclei. The nucleosome "core" structures were similar, but the spacing of the nucleosomes in the isolated polymoma nucleoprotein complexes was irregular, whereas in mouse chromatin it was regular. The average nucleosome repeat length in each case was 190 to 200 base pairs. This figure suggests that, unless there are substantial stretches of free DNA, the polyoma nucleoprotein complex contains about 26 nucleosomes. The commonly used method of preparing the nucleoprotein complex by disruption of virions at pH 10.2 may lead to significant damage to the structure. Such damage may be more clearly revealed by the susceptibility of the DNA to nuclease digestion than by the usual criteria of sedimentation velocity and buoyant density.
Insights
Polyoma virus nucleoprotein complexes and mouse chromatin share similar nucleosome core structures. However, polyoma complexes exhibit irregular nucleosome spacing, unlike regular spacing in mouse chromatin.
Area of Science:
- Molecular Biology
- Virology
- Chromatin Structure
Background:
- Nucleoprotein complexes are fundamental to viral and cellular DNA organization.
- Understanding the structural integrity of isolated viral nucleoprotein complexes is crucial for accurate biological interpretation.
Purpose of the Study:
- To compare the nucleosome structure of polyoma virus nucleoprotein complexes with mouse chromatin.
- To assess the impact of preparation methods on the structural integrity of polyoma virus nucleoprotein complexes.
Main Methods:
- Digestion of polyoma virus nucleoprotein complexes and mouse chromatin using micrococcal nuclease and DNase I.
- Analysis of DNA fragments to determine nucleosome structure and spacing.
- Comparison of nuclease digestion susceptibility with sedimentation velocity and buoyant density.
Main Results:
- Nucleosome core structures were found to be similar between polyoma virus and mouse chromatin.
- Irregular nucleosome spacing was observed in isolated polyoma virus nucleoprotein complexes, contrasting with regular spacing in mouse chromatin.
- An average nucleosome repeat length of 190–200 base pairs was estimated for both, suggesting approximately 26 nucleosomes in the polyoma complex.
Conclusions:
- The standard preparation method (pH 10.2 disruption) may damage polyoma virus nucleoprotein complexes.
- Nuclease digestion susceptibility offers a sensitive indicator of structural damage in viral nucleoprotein complexes.