7. Presence of sigma factor (σ70) in Escherichia colt facilitates
(1) Sequence specific localization of RNA polymerase on the promoter regions of genes
(2) Phosphorylation of C-terminal tail of RNA polymerase
(3) Interaction of β-subunit of RNA polymerase with α-subunit
(4) Interaction of ω-subunit with β β’ α2, complex of RNA polymerase
The presence of sigma factor (σ⁷⁰) in Escherichia coli facilitates:
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Sequence-specific localization of RNA polymerase on the promoter regions of genes
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Phosphorylation of C-terminal tail of RNA polymerase
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Interaction of β-subunit of RNA polymerase with α-subunit
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Interaction of ω-subunit with β β’ α₂ complex of RNA polymerase
Correct Answer: (1) Sequence-specific localization of RNA polymerase on the promoter regions of genes
Explanation:
What is Sigma Factor σ⁷⁰?
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σ⁷⁰ (RpoD) is the primary sigma factor in E. coli used during exponential growth.
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It is part of the RNA polymerase holoenzyme (core enzyme + sigma factor).
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Its main job is to enable specific binding to bacterial promoters and initiate transcription of housekeeping genes.
Why Option 1 is Correct:
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Sigma factor σ⁷⁰ binds to the -35 and -10 promoter regions of DNA.
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It directs RNA polymerase to these specific sequences, ensuring transcription begins at the correct site.
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Without σ⁷⁰, the core RNA polymerase cannot recognize promoter regions with high specificity.
Why Other Options Are Incorrect:
| Option | Statement | Why It’s Incorrect |
|---|---|---|
| 2 | Phosphorylation of RNA polymerase tail | This is a feature of eukaryotic RNA Pol II, not E. coli |
| 3 | β-subunit with α-subunit interaction | These interactions happen within the core enzyme, not involving sigma |
| 4 | ω-subunit interaction with ββ’α₂ complex | Again, this is about core enzyme assembly, σ⁷⁰ is not involved |
Key Concept Recap for CSIR NET:
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σ⁷⁰ = directs RNA polymerase to housekeeping promoters
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Recognizes -35 (TTGACA) and -10 (TATAAT) consensus sequences
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Dissociates after transcription initiation begins
CSIR NET Prep Tip:
Remember the core enzyme (α₂ββ′ω) lacks promoter specificity. It needs σ⁷⁰ for accurate promoter recognition and transcription start site selection.
Master Transcription with Let’s Talk Academy
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Topic-wise video explanations of bacterial gene regulation
-
Practice modules for RNA polymerase, sigma factors, and promoter architecture
-
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32 Comments
Rani Sharma
May 28, 2025✅✅
Suman bhakar
May 28, 2025✅✅
Krishana
May 28, 2025Done sir
Pallavi gautam
May 28, 2025👍👍
Arushi
May 28, 2025👍☑️
Beena Meena
May 28, 2025Done
Shalu Choudhary
May 28, 2025✅✅
Prami Masih
May 29, 2025👍✅✅✅✅
Shreeji Charan
June 1, 2025👍
Riya
June 2, 2025Perfect Explanation
Kirti Agarwal
October 26, 2025Main job of sigma 70 is to enable specific binding to bacterial promoters and initiate transcription
Santosh Saini
October 26, 2025Sigma 70 in E coli facilitates → sequence -specific localisation of RNA polymerase on the promoter regions of genes
Roopal Sharma
November 3, 2025Sigma 70 in E .coli facilitates- sequence specific localisation of RNA polymerase on the promoter regions of gemes.
Heena Mahlawat
November 3, 2025Sigma 70 in e coli facilities sequence -specific localisation of RNA polymerase on the promoter of genes
Pooja
November 3, 2025Option a is correct
anjani sharma
November 3, 2025Answer a
Sigma 70 – specific binding to bacterial promoters and initiate transcription .
Anurag Giri
November 3, 2025The correct answer option 1 Sigma 70 – specific binding to bacterial promoters and initiate transcription .
Divya rani
November 3, 2025Sigma 70 in E.coli facilitates the sequence specific localisation of RNA pol. on promotor region of gene.
Priya dhakad
November 3, 2025Ans -Sigma 70 in E .coli facilitates- sequence specific localisation of RNA polymerase on the promoter regions of gene.
Bhawna Choudhary
November 3, 2025👍👍
Mohd juber Ali
November 3, 2025Sigma70 is general Tc factor binds at TATAAT AND TTGACA Seq and initiate Tc
Dipti Sharma
November 3, 2025Sigma 70 directs RNA polymerase to the specific sequences, ensuring transcription begins at the correct site.
Sneha .kumawat
November 3, 2025Sigma 70 is the primary sector in e coli used during expansion growth.
It’s main job to enable specific binding to bacteria promoter and initiate transcription
Dharmpal Swami
November 3, 2025Sigma factor=Sequence-specific localization of RNA polymerase on the promoter regions of genes
Anjali sharma
November 3, 2025Ans is a
Shivani
November 3, 2025Sigma 70 specific binding to bacterial promoters and initiate transcription at the correct site …so option 1st is correct
Kajal
November 4, 2025Correct Answer is (1) Sequence-specific localization of RNA polymerase on the promoter regions of genes
Rishita
November 4, 2025Sigma 70 in e coli facilities sequence -specific localisation of RNA polymerase on the promoter of genes
Deepika Sheoran
November 4, 2025Sequence specific localization of RNA polymerase on the promoter regions of genes.
Manisha choudhary
November 5, 2025RNA polymerase -2 subunits function
Alpha= polymerization ,C terminal domain of alpha subunit binds with up element of strong promoter
Beta = nucleotide binding
Beta’ =DNA binding
omega = stability
Sigma factor promoter ho recognise krta h RNA polymerase ki affinity bdhata h towards promoter
Option 1 is correct answer
sigma factor= part of holo enzyme
MOHIT AKHAND
November 9, 2025Done sir ✅
Neelam Sharma
November 13, 2025Correct Answer is (1) Sequence-specific localization of RNA polymerase on the promoter regions of genes