title: Effects of diaminopurine and inosine substitutions on A-tract induced DNA curvature. Importance of the 3'-A-tract junction.
abstract: 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.
authors.affiliation: Center for Biomolecular Recognition, Department of Medical Biochemistry and Genetics, The Panum Institute, University of Copenhagen, Blegdamsvej 3c, 2200 Copenhagen N, Denmark.
authors.forename: N E
authors.initials: NE
authors.lastname: Mollegaard
authors.forename: C
authors.initials: C
authors.lastname: Bailly
authors.forename: M J
authors.initials: MJ
authors.lastname: Waring
authors.forename: P E
authors.initials: PE
authors.lastname: Nielsen
mesh_terms: D015075:2-Aminopurine / Q000031:analogs & derivatives* / Q000737:chemistry; D000225:Adenine / Q000737:chemistry; D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D015246:Deoxyribonuclease EcoRI; D015252:Deoxyribonucleases, Type II Site-Specific; D004591:Electrophoresis, Polyacrylamide Gel; D007288:Inosine / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D010777:Photochemistry; D016133:Polymerase Chain Reaction; D012091:Repetitive Sequences, Nucleic Acid; D013329:Structure-Activity Relationship; D014502:Uranyl Nitrate
chemical_list: D014502:Uranyl Nitrate; D015075:2-Aminopurine; C007300:2,6-diaminopurine; D007288:Inosine; D004247:DNA; D015246:Deoxyribonuclease EcoRI; C025630:CAGCTG-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific; D000225:Adenine