ELECTRON-MICROSCOPIC STUDIES ON CIRCULAR DNA COMPACTION IN MODEL SYSTEMS .1. COMPACT STRUCTURES OF TRIVALINE COMPLEXES WITH CIRCULAR DNA CONTAINING BENDS

An electron-microscopic study was made of the structure of complexes b etween a synthetic peptide trivaline dansylhydrazide with circular sup ercoiled plasmid DNA containing one or several regions with sequences that cause bends. The gene-engineered constructs were based on pBluesc ript II KS+ and contained fragments of minicircles from Leishmania gym nodactili with one bend (pLg-19) and Trypanosoma boissoni with four be nds (pTbo-1). The bends proved to have no essential effect on compacti on of such complexes, which gave rise to circular compact structures i dentical to the triple rings described earlier for pBR322. Nonetheless , there were some peculiarities that could be associated with the pres ence of bends, The dimeric pTbo-1 molecules, alongside with triple rin gs, produced structures with two and more linked circular regions not described heretofore. The data obtained testify to the possibility of independent compaction of separate regions in one molecule upon intera ction with trivaline. The possible role of bends in the formation of u nusual compact DNA structures is discussed.