Which of the following is a method of investigating the sequence specificity of DNbinding proteins in vitro?
Which of the following is a method of investigating the sequence specificity of DNbinding proteins in vitro?
Select an option to attempt
Correct Answer: Option D
Explanation
DNase I footprinting is used to identify the exact DNA sequence to which a protein binds. Method: (1) End-label the DNA fragment; (2) Incubate with the DNA-binding protein; (3) Treat with DNase I, which cleaves unprotected DNA at random positions; (4) Remove protein and run the DNA fragments on a gel. Where the protein was bound, DNase I cannot access — this region is 'protected' from cleavage and appears as a gap (footprint) in the ladder of bands. Comparing protein-bound vs. unbound lanes reveals the exact binding site sequence.