Molecular Biology of the Gene 7th Edition by Richard Losick, James Watson, Michael Levine, Tamara Baker, Alexander Gann

Exercise 12

You decide to study three proteins-Protein A, Protein B, Protein C-with potential roles in transcriptional regulation in mammalian cells. You perform an electrophoretic mobility shift assay (EMSA). The data is shown below. For review of this technique, see Chapter 7. All reactions contained binding buffer and labeled DNA fragment that included the sequence for the DNA-binding site for Protein A, a sequence upstream of a mammalian gene. The added purified protein(s) are indicated above the gel.
A. Based on this data, does Protein A bind DNA? Explain your answer.
B. Provide an explanation for the result observed in lane 5. Use the data in lane 2 as well in your explanation.
C. Propose a model for how Protein B potentially activates transcription.