Effects of methylation on a synthetic polynucleotide: the B--Z transition in poly(dG-m5dC).poly(dG-m5dC).

AUTOR(ES)

Behe, M

RESUMO

We have compared the behavior in solution of the synthetic polynucleotide poly(dG-m5dC).poly(dG-m5dC) with that of the unmethylated polynucleotide poly(dG-dC).poly(dG-dC). In solutions containing high concentrations of salt, poly(dG-dC).poly(dG-dC) is known to exhibit altered circular dichroic and absorption spectra correlated with formation of a left-handed Z DNA structure. Poly(dG-m5dC).poly(dG-m5dC) behaves similarly, but the spectral transition from the B to the Z form occurs at much lower salt concentrations, close to usual physiological conditions. Divalent and polyvalent ions are particularly effective: The B--Z transition of poly(dG-m5dC).(dG-m5dC) can be induced at a Mg2+ concentration three orders of magnitude lower than that required for the unmethylated polymer. We have also studied mixed copolymers containing both dC and m5dC. Our results suggest that the sequence m5dC-dG, which occurs in eukaryotic DNA, can have a disproportionately large effect on the B--Z transition.

Documentos Relacionados

• Effect of the B--Z transition in poly(dG-m5dC) . poly(dG-m5dC) on nucleosome formation.
• Conformational lability of poly(dG-m5dC):poly(dG-m5dC).
• Critical amount of oligovalent ion binding required for the B-Z transition of poly (dG-m5dC).
• Length changes in solution accompanying the B-Z transition of poly (dG-m5dC) induced by Co(NH3)63+.
• Thermodynamics of the B to Z transition in poly(m5dG-dC).