Question

The antibiotic rifampicin blocks transcription in many bacteria. In the presence of the antibiotic, adding sigma factor has no stimulating effect on RNA synthesis. A footprinting experiment on a rifamycin treated sample shows that the polymerase remains located at the promoter site in the presence of eNTPs and Mg2 ion. What step of transcription is rifamycin likely to block

Answer 1

transcription initiation

Step-by-step explanation:

Transcription is a process by which genetic information from DNA is used to synthesize an RNA molecule, usually, a messenger RNA (mRNA), which is subsequently utilized to synthesize a protein by a process called translation. Transcription in prokaryotes has three steps:

1-Initiation: the RNA polymerase is a multisubunit enzyme (holoenzyme) composed of two α, one β, one β’ and one ω and σ subunits (α2ββ’ωσ). This holoenzyme binds to the promoter region of the template DNA strand.

2-Elongation. The sigma σ factor of the holoenzyme is released and the complex and the core enzyme (α2 ββω) moves along the template strand, thereby producing an mRNA sequence

3-Termination. This step can be Rho-dependent, where a protein named "Rho" recognizes the termination site and stop transcription, and Rho-independent (transcription continues until the termination sequence is reached).

In consequence, Rifamycin is likely to block the initiation of transcription because the core RNA enzyme needs to bind the sigma factor (σ) for initiation of transcription in bacteria.