A sigma factor (σ factor or specificity factor) is a protein needed for initiation of transcription in bacteria. [1] [2] It is a bacterial transcription initiation factor that enables specific binding of RNA polymerase (RNAP) to gene promoters. It is homologous to archaeal transcription factor B and to eukaryotic factor TFIIB. [3]

Sigma factors are multi-domain subunits of bacterial RNA polymerase (RNAP) that play critical roles in transcription initiation, including the recognition and opening of promoters as well as the initial steps in RNA synthesis.

Sigma factors are subunits of all bacterial RNA polymerases that are responsible for determining the specificity of promoter DNA binding and efficient initiation of RNA synthesis (transcription). The first sigma factor discovered was the sigma70 (σ70) of the highly studied bacterium Escherichia coli.

2024年11月23日 · Sigma factor proteins promote binding of RNA polymerase to promoter sites within DNA sequences to allow for initiation of transcription. Sigma factors are specific for the gene and are affected by the cellular environment. Sigma factors can regulate at both a transcription and translational level.

Protein sigma, commonly referred to in the context of sigma factors, is a vital component of RNA polymerase in prokaryotic cells. These proteins are essential for initiating transcription, which is the first step in expressing genes.

Sigma (σ) factors are small proteins that associate with the RNA polymerase (RNAP) ‘core’ enzyme and determine what promoter the resulting ‘holoenzyme’ will recognize (Figure 7). The core RNAP (abbreviated as E) is made up of four polypeptides, α 2ββ′.

Although the RNAP core is catalytically competent for RNA synthesis, the selectivity of transcription initiation requires a sigma (σ) factor for promoter recognition and opening.

2003年4月1日 · Members of the σ70 family of sigma factors are components of the RNA polymerase holoenzyme that direct bacterial or plastid core RNA polymerase to specific promoter elements upstream of the transcription-initiation points.

2003年1月3日 · Members of the σ 70 family of sigma factors are components of the RNA polymerase holoenzyme that direct bacterial or plastid core RNA polymerase to specific promoter elements that are situated 10 and 35 base-pairs upstream of transcription-initiation points.

2021年10月18日 · In 1970, soon after our sigma work, Geoffrey Zubay discovered a new protein, cyclic AMP receptor protein or catabolite gene activator protein, that mediates the classical glucose effect and is needed for high-level expression of the lac operon and many other genes .