Transcription Termination: Hairpin vs Rho Factor

Termination Mode

Controls

Elongation rate 30 nt/s

Hairpin stability (ΔG) 60%

Rho translocation rate 40 nt/s

Live Readouts

Transcript length

0 / 120 nt

RNAP state

Elongating

Hairpin ΔG stability

60%

How it works

RNA polymerase (RNAP) elongates RNA 5'→3' by reading the DNA template inside a ~9 bp transient RNA-DNA hybrid ("transcription bubble"). Termination releases the finished transcript and the enzyme — two mechanisms do it very differently:

Intrinsic (Rho-independent):
  GC-rich inverted repeat → RNA folds into a hairpin
  right behind RNAP, followed by a weak rU·dA run.
  Hairpin invades the hybrid → RNAP pauses → the
  weak rU·dA tract lets the hybrid fray → release.

Rho-dependent:
  Rho (hexameric ATPase) loads onto a C-rich, unstructured
  "rut" site on the nascent RNA, then translocates 5'→3'
  along the RNA using ATP hydrolysis. If it catches a
  paused RNAP before the transcript ends, it unwinds the
  hybrid and pulls the RNA free.

Elongation rate — how fast RNAP adds nucleotides (nt/s); a rough proxy for how much time Rho has to catch up.
Hairpin stability (ΔG) — higher values mean a more stable hairpin: longer RNAP pause at the terminator and a higher chance the weak hybrid actually breaks instead of reading through.
Rho translocation rate — how fast the Rho ring runs along the RNA once it loads at the rut site (~nt 25); if it never reaches RNAP before the template ends, transcription reads through.
A shallow natural pause site around nt 70 is included in Rho mode — real Rho-dependent terminators lean on RNAP pausing to give the trailing ATPase a chance to close the gap.

Real-world relevance: intrinsic terminators dominate in bacteria and need no accessory factor; Rho-dependent termination also silences pervasive antisense/upstream transcription and couples termination to translation via the ribosome's own speed.

DNA duplex Nascent RNA RNA polymerase Hairpin Rho factor

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.

Transcription Termination: Intrinsic Hairpin vs Rho Factor