Question

Thank you to whoever can help me on this.

Shown below are results from an immunoprecipitation/immunoblotting experiment. Cell lysates were immuno-precipitated with ErbB-2 or a control (mIgG) antibody and immunoblotted with antibodies to importin β1 or to ErbB-2 as shown in Figure.
ErbB-2: a receptor found on the plasma membrane of mammalian cells have been shown to move from the plasma membrane to the nucleus.
Various RNA interference (SiRNA treatments) :
-: no SiRNA; Imp: importin specific SIRNA and N.S.: Non-specific SiRNA
wild-type (WT) ErbB-2
mutant ErbB-2 lacks nuclear localization signal (ΔNLS)
Shown below are results from an immunoprecipitation/immunoblotting experiment.

Cytoplasmic Nuclear IP | |--| Importin β1 Importin B1 ErbB-2 ErbB-2

Answer the following questions:
What is the objective of experiment referring to Fig a?
What can you conclude from top panel of figure a where importin antibody is being used?
What can you conclude from bottom panel of figure a where ErbB2 antibody is being used?
What is the objective of experiment referring to Fig b?
What can you conclude from figure b?

Answer 1

A- ErbB-2 localization depends on the important B-1

B- In the top panel, it is shown that upon using the siRNA against the importin B-1 its expression level in drastically decrease which can be seen in the left panel in the cytoplasmic fragment. Since its expression drastically decreases the level of importin B-1 is nucleus has almost become negligible.

C- As we can see that upon using the siRNA of importin B-1, the levels of ErbB2 is not decreased in the cytoplasm but it was decreased in the nuclear fragment.

D- The main objective of figure B was to check if importin B-1 plays any role in the localization of ErbB2 to the nucleus.

E- It was evident from the figure B that ErbB2 binds to the importin via its NLS. When NLS was deleted ErbB2 was failed to localize in the nucleus