Two Segments (S1 and S2) in a Viral Protein Are

Multiple Choice

Two segments (S1 and S2) in a viral protein are suspected to be responsible for the nuclear localization of the protein in infected human cells. You have engineered a plasmid to encode the green fluorescent protein (GFP) fused to either or both of these peptide segments, and have introduced the plasmid into the cells. After the expression of the fusion protein is induced, you visualize the cells using a fluorescence microscope equipped with filters appropriate for detection of GFP. Your results are presented in the following schematic drawings in which the GFP signal is represented in green. Which of the following is more consistent with these observations?

A) Both S1 and S2 are required for nuclear localization.
B) S1 is required and sufficient for nuclear localization.
C) S2 is required and sufficient for nuclear localization.
D) S1 is required but not sufficient for nuclear localization.
E) S2 is required but not sufficient for nuclear localization.