σ factor

Definition

σ factor is a protein needed for the initiation of transcription in bacteria. It enables RNA polymerase to bind to specific promoter regions on DNA.

5 Must Know Facts For Your Next Test

1. σ factor helps RNA polymerase recognize and bind to promoters.
2. Different σ factors recognize different sets of promoters, allowing for differential gene expression.
3. The primary σ factor in E. coli is σ70, which recognizes most housekeeping genes' promoters.
4. Alternative σ factors are used during specific conditions, such as heat shock or nitrogen starvation.
5. σ factors dissociate from RNA polymerase after the initiation of transcription, allowing elongation to proceed.

Review Questions

• What role does the σ factor play in bacterial transcription?
• How do alternative σ factors contribute to gene regulation?
• Why does the σ factor dissociate from RNA polymerase after transcription initiation?

Related terms

RNA Polymerase:

An enzyme that synthesizes RNA from a DNA template.

Promoter:

A DNA sequence that initiates gene transcription by providing a binding site for RNA polymerase and associated proteins like the σ factor.

Operon:

A cluster of genes under the control of a single promoter, transcribed into a single mRNA molecule.