[Visualization of bacteriophage T7 RNA-polymerase complexes with DNA template in the process of transcription...

Complexes of bacteriophage T7 RNA polymerase (T7 RNAP) with a DNA template (which contains a promoter and internal terminator of T7 RNAP) in transcription elongation were visualized by atomic force microscopy (AFM). Images of specific stable complexes of T7 RNAP with a terminal fragment of DNA template located at a distance of 200 bp from the T7 RNAP promoter were obtained for single molecules. Complexes of a single DNA template molecule with 2-3 T7 RNAP molecules corresponding to stages of initiation, elongation and termination of transcription were visualized under the elimination of nonspecific DNA-protein binding. Detailes of specific and nonspecific complex formation for the T7 RNAP--DNA system during initiation and transcription elongation are discussed.