期刊
BIOCHIMICA ET BIOPHYSICA ACTA-GENERAL SUBJECTS
卷 1527, 期 1-2, 页码 73-80出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/S0304-4165(01)00150-7
关键词
DNA conformational polymorphism; circular dichroism; Z-DNA; parallel-stranded DNA; trinucleotide repeat DNA
Conformational properties of microsatellite DNA regions are the probable reason of their expansions in genomes which lead to serious genetic diseases in some cases. Using CD spectroscopy, W absorption spectroscopy and polyacrylamide gel electrophoresis, we study in this paper conformational properties of (CGA)(4) and compare them with those of (CAG)(4) - a related repeat. connected with Huntington's disease. We show that (CGA)(4) can adopt several distinct conformations in solution. Around neutral pH it forms a parallel-stranded homoduplex containing C+.C, G.G, and A.A base pairs. Under the same conditions (CAG)(4) forms a hairpin. At slightly alkaline pH values and low ionic strength, (CGA)(4) also folded into a hairpin which transformed into a bimolecular anti-parallel homoduplex at increasing salt concentrations. The duplex easily isomerized into left-handed Z-DNA, implying that the mismatched adenines between G.C pairs facilitate rather than hinder the B-Z transition. No similar changes took place with (CAG)(4). Thus, the conformational repertoire of (CAG)(4) includes parallel. anti-parallel, right-handed, and left-handed homoduplexes. In contrast, (CAG)(4) invariably adopts only a single conformation. namely the very stable hairpin. (C) 2001 Elsevier Science B.V. All rights reserved.
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