Domain architecture of eukaryotic transcriptional activators: They usually contain which structural features?

Introduction / Context:
Many eukaryotic transcriptional activators are modular proteins that bind specific DNA sequences and recruit coactivators or the basal transcription machinery to enhance gene expression.

Given Data / Assumptions:

• Activators typically have separable domains.
• DNA-binding and activation functions can be experimentally reassorted.

Concept / Approach:
A canonical activator includes a DNA-binding domain (zinc finger, bZIP, bHLH, etc.) and an activation domain (acidic, glutamine-rich, proline-rich) that interacts with coactivators such as Mediator or histone-modifying enzymes.

Step-by-Step Solution:
Identify the minimal modular requirement → DNA-binding + activation. Exclude options lacking activation capacity or modularity. Select the statement reflecting two-domain architecture.

Verification / Alternative check:
Domain-swap experiments show that activation domains can function when fused to unrelated DNA-binding domains.

Why Other Options Are Wrong:
Options without activation domains cannot stimulate transcription; claiming no modularity contradicts extensive biochemical data.

Common Pitfalls:
Confusing activation domains with general transcription factors; overlooking coactivator recruitment.

Final Answer:
At least two distinct domains: a DNA-binding domain and an activation domain.