DNA structural features responsible for sequence-dependent binding geometries of Hoechst 33258

Jin Hee Moon, Seog K. Kim*, Ulrica Sehlstedt, Alison Rodger, Bengt Nordén

*Corresponding author for this work

Research output: Contribution to journalArticle

57 Citations (Scopus)

Abstract

The complexes of Hoechst 33258 with poly[d(A-T)2], poly[d(I-C)2], poly[d(G-C)2], and poly[d(G-m5C)2] were studied using linear dichroism, CD, and fluorescence spectroscopies. The Hoechst-poly[d(I-C)2] complex, in which there is no guanine amino group protruding in the minor groove, exhibits spectroscopic properties that are very similar to those of the Hoechstpoly[d(A-T)2] complex. When bound to both of these polynucleotides, Hoechst exhibits an average orientation angle of near 45° relative to the DNA helix axis for the long-axis polarized low-energy transition, a relatively strong positive induced CD, and a strong increase in fluorescence intensity - leading us to conclude that this molecule also binds in the minor groove of poly[d(I-C)2]. By contrast, when bound to poly[d(G-C)2] and poly[d(G-m5C)2], Hoechst shows a distinctively different behavior. The strongly negative reduced linear dichroism in the ligand absorption region is consistent with a model in which part of the Hoechst chromophore is intercalated between DNA bases. From the low drug : base ratio onset of excitonic effects in the CD and fluorescence emission spectra, it is inferred that another part of the Hoechst molecule may sit in the major groove of poly[d(G-C)2] and poly[d(G-m5C)2] and preferentially stacks into dimers, though this tendency is strongly reduced for the latter polynucleotide Based on these results, the importance of the interactions of Hoechst with the exocyclic amino group of guanine and the methyl group of cytosine in determining the binding modes are discussed.

Original languageEnglish
Pages (from-to)593-606
Number of pages14
JournalBiopolymers
Volume38
Issue number5
Publication statusPublished - 1996
Externally publishedYes

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