Practice question

Yeast two-hybrid exploits the modular architecture of eukaryotic transcription factors, typically Gal4, which has separable DNA-binding and activation functions. Bait, the known protein, is fused to the DNA-binding domain to tether it to the upstream activating sequence of reporter genes. This fusion alone cannot activate transcription. When prey fused to activation domain interacts with bait, the two domains are brought into proximity, reconstituting a functional activator that drives transcription of auxotrophic or colorimetric reporters, enabling detection of interaction in vivo.