Question

You are interested in understanding the gene regulation of Lkp1, a protein that is normally produced in liver and kidney cells in mice. You find that LKP1 gene is not expressed in heart cells. You isolate the DNA upstream of the gene, and place it upstream of the gene for GFP and insert this entire piece of recombinant DNA into mice. You find GFP expressed in liver and kidney cells. Experiments demonstrate that there are three regions in the promoter labeled, A, B, and C that contribute to this expression pattern. Assume that a single transcription factor binds each site such that protein X binds site A, protein Y binds site B, and protein Z binds site C. Determine which region is responsible for tissue-specific expression and what the function of each region is. If the site is missing, it is mutated such that it cannot bind its corresponding transcription factor.

Which of the following proteins are likely to act as gene ACTIVATORS?
(a) factors X and Y
(b) factors X and Z
(c) factors Y and z
(d) factor X only

Answer 1

Region B is responsible for tissue-specific expression, with regions A and C having different functions. Factors X and Y are likely to act as gene activators in this experiment.

Step-by-step explanation:

The region responsible for tissue-specific expression in the experiment described is region B in the promoter of the Lkp1 gene. This is because when region B is mutated and cannot bind its corresponding transcription factor protein Y, LKP1 gene expression is affected and GFP is not expressed in the liver and kidney cells. The function of region A is to bind the transcription factor protein X, and the function of region C is to bind the transcription factor protein Z.

The likely gene activators in this scenario are factors X and Y because when these factors bind their respective sites A and B in the promoter region, GFP is expressed in the liver and kidney cells. Factor Z is not likely to act as a gene activator because its binding site C is not responsible for tissue-specific expression.