HENRY M. SOBELL

A MECHANISM TO UNDERSTAND THE B- TO Z- TRANSITION



(Above, left). Dislocaton pairs form from actively breathing premeltons within B-DNA regions and then move apart, leaving growing B-DNA regions behind. The model predicts single chain slippage events to involve an even number of nucleotide bases. This sequence of events can also occur with A-DNA or A-RNA containing the appropriate (even numbered) repetitive base sequences.

(Above, right). Dislocaton pairs form from actively breathing premeltons within B-DNA regions and then move apart, leaving growing Z-DNA regions behind. Again, the model predicts single chain slippage events to involve an even number of nucleotide bases. This sequence of events can also occur in A-DNA or A-RNA containing the appropriate (even numbered) repetitive base sequences.


The B- to Z- transition arises as the result of a bifurcation that takes place during the formation of the dislocaton. A fundamental prediction of the model is the appearance of single-stranded DNA regions juxtaposed to beta-DNA regions within each B-Z junction. The model predicts S1 nuclease sensitive sites to lie within the junctions, and predicts high cooperatively to accompany ethidium binding. Both predictions are supported by experimental data. See text for additional discussion.