[Visualization of elongation complexes for t7 Rna polymerase by atomic force microscopy].

Area of Science:

• Molecular Biology
• Biophysics

Context:

• Bacteriophage T7 RNA polymerase (RNAP) plays a crucial role in gene expression.
• Understanding the dynamics of RNAP-DNA interactions is essential for deciphering transcription regulation.

Purpose:

• To visualize and characterize the structural complexes formed between bacteriophage T7 RNA polymerase and its DNA template during transcription using atomic force microscopy (AFM).

Summary:

• Atomic force microscopy (AFM) was employed to image single-molecule complexes of bacteriophage T7 RNA polymerase (RNAP) with a linear DNA template containing promoter and terminator elements.
• Stable complexes were visualized at various stages of transcription, including initiation, elongation, and termination, by eliminating non-specific DNA-protein binding.
• The study observed complexes of DNA with 2-3 RNAP molecules and RNA transcripts, suggesting that initial complex formation occurs at the DNA template's terminal fragment near the promoter.

Impact:

• Provides direct visualization of transcription complex formation and dynamics at the single-molecule level.
• Offers insights into the mechanism of transcription initiation and elongation by bacteriophage T7 RNAP.
• Highlights the importance of promoter proximity to the DNA terminus in ensuring efficient transcription initiation.