Estimating RNA Polymerase Protein Binding Sites on λ DNA Using Solid-State Nanopores

Area of Science:

• Molecular Biology
• Nanotechnology
• Biophysics

Background:

• Understanding transcription factor binding is crucial for gene regulation.
• Accurate mapping of RNA Polymerase (RNAP) on long DNA molecules presents technical challenges.

Purpose of the Study:

• To measure the binding locations and efficiency of RNAP on long lambda DNA using a nanopore device.
• To investigate the feasibility of using nanopore technology for studying protein-DNA interactions.

Main Methods:

• Utilized a silicon nitride nanopore device to detect current blockage events caused by RNAP bound to lambda DNA.
• Employed formaldehyde cross-linking to secure RNAP to DNA during high electric field measurements.
• Analyzed current signal durations, amplitudes, and subevent timing to estimate binding parameters.

Main Results:

• Determined a RNAP binding probability of approximately 42% on lambda DNA at a 6:1 RNAP to DNA ratio.
• Identified a main RNAP binding peak at 3.51 μm ± 0.53 μm on the 16.5 μm lambda DNA molecule.
• Observed that individual RNAP binding sites could not be resolved with the current nanopore setup.

Conclusions:

• Nanopore technology offers a novel approach for studying RNAP binding on long DNA molecules.
• The study provides insights into RNAP binding efficiency and preferred locations, correlating with known promoter regions.
• Further refinement of nanopore resolution is needed to distinguish individual binding sites.