Related Experiment Videos
Cleavage of chromatin with methidiumpropyl-EDTA . iron(II)
Abstract:
Methidiumpropyl-EDTA . iron(II) [MPE . Fe (II)] cleaves double-helical DNA with considerably lower sequence specificity than micrococcal nuclease. Moreover, digestions with MPE . Fe(II) can be performed in the presence of certain metal chelators, which will minimize the action of many endogenous nucleases. Because of these properties MPE . Fe(II) would appear to be a superior tool for probing chromatin structure. We have compared the patterns generated from the 1.688 g/cm3 complex satellite, 5S ribosomal RNA, and histone gene sequences of Drosophila melanogaster chromatin and protein-free DNA by MPE . Fe(II) and micrococcal nuclease cleavage. MPE . Fe(II) at low concentrations recognizes the nucleosome array, efficiently introducing a regular series of single-stranded (and some double-stranded) cleavages in chromatin DNA. Subsequent S1 nuclease digestion of the purified DNA produces a typical extended oligonucleosome pattern, with a repeating unit of ca. 190 base pairs. Under suitable conditions, relatively little other nicking is observed. Unlike micrococcal nuclease, which has a noticeable sequence preference in introducing cleavages, MPE . Fe(II) cleaves protein-free tandemly repetitive satellite and 5S DNA sequences in a near-random fashion. The spacing of cleavage sites in chromatin, however, bears a direct relationship to the length of the respective sequence repeats. In the case of the histone gene sequences a faint, but detectable, MPE . Fe(II) cleavage pattern is observed on DNA, in some regions similar to and in some regions different from the strong chromatin-specified pattern. The results indicate that MPE . Fe(II) will be very useful in the analysis of chromatin structure.
Insights
Methidiumpropyl-EDTA iron(II) (MPE . Fe (II)) offers a superior method for probing chromatin structure compared to micrococcal nuclease. Its ability to cleave DNA with lower sequence specificity and in the presence of chelators aids in chromatin analysis.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Chromatin structure analysis is crucial for understanding gene regulation.
- Existing DNA cleavage tools like micrococcal nuclease have limitations in sequence specificity and nuclease inhibition.
- Methidiumpropyl-EDTA iron(II) (MPE . Fe (II)) has emerged as a potential alternative for DNA cleavage studies.
Purpose of the Study:
- To compare the efficacy of MPE . Fe (II) and micrococcal nuclease in probing Drosophila melanogaster chromatin structure.
- To evaluate the sequence specificity and cleavage patterns of MPE . Fe (II) on different DNA sequences within chromatin and protein-free DNA.
Main Methods:
- DNA cleavage assays using MPE . Fe (II) and micrococcal nuclease on Drosophila melanogaster chromatin and protein-free DNA.
- Analysis of cleavage patterns on satellite DNA, 5S ribosomal RNA genes, and histone gene sequences.
- Subsequent S1 nuclease digestion to analyze oligonucleosome patterns.
Main Results:
- MPE . Fe (II) recognizes the nucleosome array, introducing regular cleavages in chromatin DNA, yielding an oligonucleosome repeat of approximately 190 base pairs.
- Unlike micrococcal nuclease, MPE . Fe (II) exhibits near-random cleavage on protein-free repetitive DNA sequences.
- Cleavage site spacing by MPE . Fe (II) in chromatin correlates with the length of sequence repeats, with detectable patterns observed even in histone gene regions.
Conclusions:
- MPE . Fe (II) is a valuable tool for chromatin structure analysis due to its lower sequence specificity and ability to function with metal chelators.
- The cleavage patterns generated by MPE . Fe (II) provide insights into DNA organization within chromatin, particularly the nucleosome array.
- MPE . Fe (II) offers a complementary approach to micrococcal nuclease for detailed chromatin structural studies.