DNA bending in the replication zone of the C3 DNA puff amplicon of Rhynchosciara americana (Diptera: Sciaridae).

Intrinsic bent DNA sites were identified in the 4289 bp segment encompassing the replication zone which directs DNA amplification and transcription of the C3-22 gene of Rhynchosciara americana. Restriction fragments showed reduced electrophoretic mobility in polyacrylamide gels. The 2D modeling of the 3D DNA path and the ENDS ratio values obtained from the dinucleotide wedge model of Trifonov revealed the presence of four major bent sites, positioned at nucleotides -6753, -5433, -5133 and -4757. Sequence analysis showed that these bends are composed of 2-6 bp dA.dT tracts in phase with the DNA helical repeat. The circular permutation analysis permitted the verification that the fragments containing the bending sites promote curvature in other sequence contexts. Computer analyses of the 4289 bp sequence revealed low helical stability (DeltaG values), negative roll angles indicating a narrow minor groove and a putative matrix attachment region. The data presented in this paper add to information about the structural features involved in this amplified segment.