Typical eukaryotic transcription factors, such as GAL4 and GCN4, all contain two different domains: DNA binding domain and transcription activation domain.

The former can identify specific sequences on DNA and locate the transcriptional activation domain upstream of the regulated gene. Transcription activation domain can interact with other components of transcription complex to start transcription of genes it regulates.

Extended data:

The yeast two-hybrid system can determine the binding of protein in vivo with high sensitivity. The main reasons are:

1. An expression vector with high copy and strong promoter is used to overexpress hybrid proteins.

2. The signal measurement is carried out under the condition of natural equilibrium concentration, but physical methods such as immunoprecipitation need to be washed many times to reach this condition, which reduces the signal intensity.

3. The stability between hybrid proteins can be enhanced by the combination of activation domain and binding domain to form transcription initiation complex, which in turn binds to promoter DNA. This ternary complex makes the combination of all components tend to be stable.

4.mRNA produces a variety of stable enzymes to amplify signals. At the same time, the detection methods of yeast phenotype, X-Gal and HIS3 protein expression are very sensitive.

In the process of studying the structural and functional characteristics and mode of action of protein, it is sometimes necessary to destroy the interaction between protein by mutation and adding inhibitors. In view of this need in practical work, Vidal and others developed the so-called reverse two-hybrid system.

The key of this technology is the introduction of reporter gene URA3. URA3 gene plays an anti-selection role here, and the enzyme it encodes is the key enzyme for uracil synthesis.

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