Reciprocating RNA Polymerase batters through roadblocks.

Area of Science:

• Molecular biology
• Biophysics

Background:

• RNA polymerases (RNAPs) are essential enzymes that transcribe DNA into RNA.
• RNAP must navigate protein-DNA roadblocks during transcription to produce full-length RNA molecules.
• Understanding RNAP-roadblock interactions is crucial for comprehending gene regulation and transcription efficiency.

Approach:

• Real-time measurements of Escherichia coli (E. coli) RNAP passage through protein roadblocks (LacI) were conducted.
• Applied forces (assisting and opposing) were used to probe RNAP translocation dynamics.
• Experiments were performed with and without GreA, a protein that rescues backtracked RNAP.

Key Points:

• Assisting forces facilitated RNAP passage, while opposing forces hindered it under normal conditions.
• Opposing forces promoted RNAP passage when backtracking rates were high, particularly with GreA present.
• RNAP may transit roadblocks via dissociation or cycles of backtracking, recovery, and ramming.

Conclusions:

• RNAP translocation through roadblocks is a complex process influenced by force and backtracking dynamics.
• Reciprocating motion of RNAP may facilitate passage through roadblocks and protein-DNA contacts.
• This mechanism could be vital for promoter escape and productive RNA elongation in vivo.