Effects of diaminopurine and inosine substitutions on A-tract induced DNA curvature. Importance of the 3'-A-tract junction.

AUTOR(ES)

Mollegaard, N E

RESUMO

Gel migration and uranyl photoprobing have been used to study the effects of inosine and 2,6-diaminopurine (2,6-DAP) substitution on adenine-tract (A-tract) induced DNA curvature. Using a 10mer repeated sequence including five inosines we show by uranyl photoprobing that a narrow minor groove varying in phase with the helix repeat is not the cause of DNA curvature. Further, we have systematically studied by gel migration the effects on A-tract induced curvature of either single or full substitution with inosine and/or 2,6-DAP in a 5'-AAAAAGCCGC-3'sequence. DNA curvature is shown to increase when inosines are substituted for the guanosines in the sequence between the A-tracts. By comparing the effects of each monosubstitution it can be seen that when the G closest to the 3'-end of the A-tract is substituted the effect on DNA curvature is much stronger than when substitution is made at any other position. By contrast, curvature is abolished when 2,6-DAP residues are substituted for all adenines, and monosubstitution reveals that the effect of substituting a single adenine is strongest at the 3'-end of the A-tract. These results favor a model in which the curvature induced by an A-tract in DNA molecules is primarily located at the junction with the 3'-end of the A-tract, and this peculiar junction is created because the A-tract has a preference to form a non-B-DNA structure which builds up from the 5'-end.

Documentos Relacionados

• The effects of sequence context on DNA curvature.
• Structure of an alternating-B DNA helix and its relationship to A-tract DNA.
• Crystal structure of CATGGCCATG and its implications for A-tract bending models.
• Detection of an unusual distortion in A-tract DNA using KMnO4: effect of temperature and distamycin on the altered conformation.
• DNA A-tract bending in three dimensions: Solving the dA4T4 vs. dT4A4 conundrum