Scientists investigated the role of a molecular chaperone called Hsp70 in stabilizing the tumor suppressor protein p53. Their research involved cell disruption followed by centrifugation and protein analysis.
The scientists lysed human cancer cells by placing them in a highly hypotonic buffer solution (osmotic shock).
Suggest how this treatment releases Hsp70, which is located in the cytoplasm, from the cells.
Explain how differential centrifugation is used to separate soluble cytosolic proteins, such as Hsp70, from larger organelles and intact cell debris.
Hsp70 acts as a molecular chaperone that binds to and stabilizes the active form of the p53 protein. In the absence of Hsp70, p53 is rapidly targeted for degradation by the cellular proteasome.
The scientists treated the cancer cell culture with small interfering RNA (siRNA) designed to target the transcripts of the Hsp70 gene. They took cell samples at 000, 121212, and 36 hours36\text{ hours}36 hours after adding the siRNA. They then used gel electrophoresis to separate and detect the Hsp70 and p53 proteins.
The image below shows the results of this analysis. The density and size of each band are proportional to the amount of Hsp70 or p53 present.
Suggest how the siRNA produced the results shown in the gel electrophoresis.
