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#reporter gene

3 public questions tagged with this topic.

Protein-Protein Interaction

What is the final output readout in yeast two-hybrid assay?

Final readout in yeast two-hybrid is based on transcriptional activation of reporter cassettes integrated downstream of Gal4-responsive promoters. If bait and prey physically associate, the activation domain is tethered to promoter, stimulating transcription of genes enabling growth on selective media lacking histidine or adenine, or colorimetric enzymes like beta-galactosidase. Thus survival, colony color, or luminescence reflects interaction strength. Fluorescence intensity, radiolabel, or sequencing are not primary outputs, although secondary validation may use them. The system converts protein interaction into a genetic readout amenable to selection.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Protein-Protein Interaction

If the bait and prey interact, which component is activated?

The readout of yeast two-hybrid depends on reconstitution of a functional transcription factor at the reporter locus. Bait-DNA-binding domain fusion and prey-activation domain fusion individually cannot activate transcription. Interaction bridges them, positioning the activation domain at upstream activating sequences of reporter genes such as HIS3, ADE2, or lacZ. This triggers recruitment of Mediator and RNA polymerase II, leading to measurable transcription. Reporter activation therefore serves as indirect but powerful evidence of protein-protein association inside living yeast nuclei under physiological conditions.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Gene Cloning Process

What type of gene is typically used as a reporter in negative selection screening?

Negative selection or insertional inactivation screening uses a reporter gene whose function is lost when foreign DNA integrates within it, allowing differentiation of recombinants from parental vectors. LacZ encoding β-galactosidase serves this purpose efficiently; intact lacZ cleaves X-gal producing blue colonies while insertion disrupts α-peptide coding, yielding white colonies. Origin of replication maintains plasmid copy number, antibiotic resistance gene AmpR provides positive selection, and T7 promoter drives transcription. Among these, only lacZ provides a scorable loss-of-function phenotype suitable as reporter for insertional disruption screening.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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