A Model for the Specific Site Melting of DNA in Vivo
While there is evidence that strand separation in DNA is an important control event for both transcription and replication (1,2) there is no specific model that would provide a satisfactory mechanistic account as to how localized helical destabilization might be initiated by a protein and be restricted to a specific DNA sequence under the highly stabilizing conditions found in vivo (3). An hypothetical model for sequence-specific destabilization can be formulated quite naturally on the basis of proton exchange mechanisms in DNA to be described in this report. This model provides for the exclusive destabilization of G-C rich sequences under the influence of polycationic sequences of proteins. Superficially, these features are contradictory to the well known stability of G-C regions and the ionic stabilization of DNA by polycations. In addition, the model contains the apparently self-contradictory notion that an increase in H-bond strength will establish the condition of destabilization. Therefore, justification of such a model will be based on close examination of a rational basis for its formulation and second on a comparison of its predictive features with several general observations on DNA melting reported in the literature.
KeywordsProton Transfer Double Helix Ionic Stabilization Imino Proton Neutral Base
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