Sequences that adopt non-B-DNA conformation in form V DNA as probed by enzymic methylation

Brahmachari, Samir K and ShoucheCharles, YS and Cantor, R and McClelland, Michael (1987) Sequences that adopt non-B-DNA conformation in form V DNA as probed by enzymic methylation. In: Journal of Molecular Biology, 193 (1). pp. 201-211.

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Abstract

pBR322 form V DNA is a highly torsionally strained molecule with a linking number of zero. We have used sequence- specific DNA methylases as probes for B-DNA in this molecule, exploiting the inability of methylases to methylate single-stranded DNA and Z-DNA, both of which are known to occur in form V DNA. Some sequences in form V DNA were shown to be totally in the B-form, others were totally in an altered, unmethylatable conformation, while still other sites appeared to exist partly in altered and partly in normal B-conformation. Some potential Z-forming sequences (alternating pyrimidine/purine) of less than seven base-pairs were not in the Z conformation in form V DNA, whereas others did adopt an altered structure, indicating a modulating influence of flanking sequences. Furthermore, regions of imperfect alternating pyrimidine/purine structure were sometimes capable of adopting an altered structure. In addition, some regions of altered structure had no apparent Z-forming sequences, nor were they in polypurine stretches, which have also been proposed to form left-handed DNA. These non-B-DNA conformations may represent novel left-handed helical structures or sequences that become single stranded under torsional strain. Long regions of either altered (unmethylatable) DNA or B-DNA were not always observed. In fact, one region showed three transitions between B-like DNA and altered structure within 26 base-pairs.

Item Type:	Journal Article
Publication:	Journal of Molecular Biology
Publisher:	Elsevier Science
Additional Information:	Copy right of this article belongs to Elsevier Science.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	15 Jan 2010 07:02
Last Modified:	19 Sep 2010 05:39
URI:	http://eprints.iisc.ac.in/id/eprint/21865

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