Chapter 20.2, Problem 1CS

Core Skill: Modeling The goal of this modeling challenge is to make a model that shows how a homeotic protein can interact with mediator.

Modeling Challenge: A gene, which we will call gene x, has an enhancer that is activated by a homeotic protein. The homedomain binds to the enhancer, as shown in Figure 20.15b. The enhancer is a long distance from the core promoter of gene X. After the homeotic protein binds to the enhancer, it interacts with mediator (refer back to Figure 14.16) to stimulate the transcription of gene X. Draw a model that shows how this homeotic protein interacts with mediator.

Figure 20.15 Molecular features of homeotic genes and proteins. (a) A homeotic gene (shown mostly in green) contains a 180-bp sequence called the homeobox (shown in blue). (b) Homeotic genes encode homeotic proteins that function as transcription factors. The homeotic protein contains two key domains called the homeodomain and the transcriptional activation domain. The homeodomain binds to the DNA at a regulatory site such as an enhancer. After this binding occurs, the transcriptional activation domain activates RNA polymerase to begin transcription.