Question

Which of the following can NOT be utilized for studying protein-protein interaction?

• A. Yeast two-hybrid system
• B. Split-ubiquitin assay
• C. Phage display
• D. SAGE

Hint:

Interactomics = Y2H, FRET, Co-IP, Split-Ub, Phage Display.
Transcriptomics = SAGE, Microarray, RNA-Seq, Northern Blot.
Think: "Does this look at Sticky Proteins or RNA Tags?"

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question requires distinguishing between techniques used to study physical interactions between proteins (the "interactome") and techniques used to measure gene transcript levels (the "transcriptome").

Step 2: Detailed Explanation:

• Yeast Two-Hybrid (Y2H) (A): A classic in vivo technique where two proteins are fused to different domains of a transcription factor. If they interact, they bring the domains together, activating a reporter gene. It is the gold standard for PPI studies.

• Split-Ubiquitin Assay (B): A variation of the two-hybrid system used specifically for membrane proteins. Interaction of proteins brings two halves of ubiquitin together, triggering a proteolytic release of a reporter.

• Phage Display (C): A technique where a library of proteins is displayed on the surface of bacteriophages. It is used to screen for proteins that bind to a specific "bait" protein, thus identifying protein-protein interactions.

• SAGE (D): Serial Analysis of Gene Expression is a high-throughput technique used to quantify the levels of mRNA (transcripts) in a cell. It involves creating small "tags" from cDNA and sequencing them. SAGE tells you about gene expression, not whether the resulting proteins physically stick to each other.

Step 3: Final Answer:
SAGE is a transcriptomics method; it cannot provide information about the physical interactions between protein molecules.