Abstract
Upon treatment with UV irradiation, native (supercoiled) PM2 DNA undergoes an increase in electrophoretic mobility relative to the nicked circular form in the presence of 1 M NaCl or 5 mM CaCl2 or MgCl2. This effect is dependent upon supercoiling in that the relative electrophoretic mobility decreases with decreasing superhelical density of the molecule. These findings indicate that supercoil-dependent aspects of the secondary and tertiary structure of nonirradiated PM2 DNA can be altered by a combination of UV irradiation and any of the ionic environments above. We show that the alteration is not the result of a conversion of Z-DNA segments to a right-handed helix or to a renaturation of denatured regions in PM2 DNA. Circular dichroism studies do not support a simple model in which A-form DNA induced by superhelical stress is converted to B-form DNA by UV-induced photodamage and salt. We, therefore, present three alternative explanations for these observations two of which invoke conformational transitions in secondary structure and a third which requires a change in tertiary structure due to an increase in flexibility.
Original language | English (US) |
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Pages (from-to) | 265-272 |
Number of pages | 8 |
Journal | BBA - Gene Structure and Expression |
Volume | 1216 |
Issue number | 2 |
DOIs | |
State | Published - Nov 16 1993 |
Keywords
- Conformational transition
- PM DNA
- Supercoiling
- Ultraviolet irradiation
ASJC Scopus subject areas
- Structural Biology
- Biophysics
- Biochemistry
- Genetics