Transcription Activation in Eukaryotic Cells

Abstract

Transcription activation is the first step in eukaryotic gene expression. Gene regulation, which is about turning on and off expression of specific protein‐coding genes in response to environmental changes, during development and in differentiated cells, widely occurs at the level of transcription activation. This is mostly achieved by DNA‐binding proteins that can control the specificity of the RNA polymerase II enzyme.

Keywords: promoters; enhancers; transcription; activators; recruitment

Figure 1.

Transcription factor requirement for specific promoter binding and transcription initiation by RNA polymerase II. (a) Purified RNA polymerase II (Pol II) has affinity for DNA but is unable to recognize promoter sequences and specifically initiate transcription. (b) General transcription factors (GTFs), including TFIID, which is composed of the TATA‐binding protein (TBP) and the associated factors (TAFs) and can interact with some of the other GTFs, help the Pol II to specifically bind promoter sequences and initiate transcription on naked DNA template in vitro. (c) Additional factors are required for specific transcription initiation and activation in vivo on DNA template that is packaged into nucleosomes (cylinder‐shaped histone octamer complexes with DNA wrapped around them). These additional factors include the Mediator complex, which interacts with Pol II, the nucleosome remodelling factors SWI/SNF and SAGA, and the sequence‐specific transcriptional activators, which are typically composed of a DNA‐binding domain (DBD) and an activation domain (AD) that can potentially interact with all the above factors to stimulate transcription. Arrows indicate potential molecular interactions, while the bent arrow on the DNA outline indicates specific initiation of transcription. The promoter region is where the transcription complex binds and transcription initiates. Enhancer is the binding site for transcriptional activators.

Figure 2.

Transcription activation by recruitment of the RNA polymerase II transcription complex. (a) A sequence‐specific DNA‐binding protein (DBD) lacking an activation domain does not activate transcription in yeast cells containing wild‐type Gal11in the Mediator complex. (b) This DNA‐binding protein becomes a strong transcriptional activator in the presence of the mutant Gal11P as part of the Mediator complex because it specifically interacts with this transcription factor and thereby recruits the entire transcription complex to the promoter. (c) The same DNA‐binding domain (DBD) directly fused to Gal11 (or to Gal11P) specifically recruits the transcription complex to the promoter and activates transcription. The TATA‐binding TFIID, which is required for this instance of transcription activation, is believed to bind the promoter cooperatively with the rest of the transcription complex when this is recruited to DNA.

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References

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Further Reading

Cramer P, Srebrow A, Kadener S, et al. (2001) Coordination between transcription and pre‐mRNA processing. FEBS Letters 498: 179–182.

Green MR (2000) TBP‐associated factors (TAFIIs): multiple, selective transcriptional mediators in common complexes. Trends in Biochemical Science 25: 59–63.

Malik S and Roeder RG (2000) Transcriptional regulation through Mediator‐like coactivators in yeast and metazoan cells. Trends in Biochemical Science 25: 277–283.

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Struhl K (1997) Selective roles for TATA‐binding‐protein‐associated factors in vivo. Genes and Function 1: 5–9.

Struhl K (1999) Fundamentally different logic of gene regulation in eukaryotes and prokaryotes. Cell 98: 1–4.

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How to Cite close
Barberis, Alcide, and Petrascheck, Michael(May 2003) Transcription Activation in Eukaryotic Cells. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0003303]