Assignment 3 - Zachary Bergman Cell Bio 315 2/1/10 1. (1...

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Zachary Bergman Cell Bio 315 2/1/10 1. (1 pt) What three distinct ways did the authors use to eliminate or almost entirely eliminate significant protein levels of the MAGUKs ZO-1, ZO-2 and ZO-3? First they started with mouse Eph4 cells in which ZO-3 was not expressed as the building block for eliminating the expression of the other two proteins. They then used homologous recombination to remove the expression of the ZO-1 protein, or knock it out (ko), in the mouse Eph4 cells which already lacked ZO-3. Finally, they used short interfering RNAs to suppress expression of the ZO-2 protein, by knocking t down (kd), on this same cell line that already lacked ZO-1 and ZO-3. The combination of these three techniques in this order allowed for the nearly complete elimination of the expression of these three proteins. 2. (1pt) Based on the data in Figure 1D, right hand side (the four confocal pictures, not the Western blots), what do you conclude about the role of ZO-3 in assembly of tight junctions? Briefly justify your answer. The ZO-3 protein seems to have little to no function in the actual assembly of the tight junctions, but instead is dependent on both ZO-1 and ZO-2 for correct positioning in the tight junction complex. This can be seen by comparing the wildtype cell line to the ZO- 1(ko)/ZO-2 (kd). In the wildtype ZO-3 is present in low amounts in the cytosol and very concentrated on the cell membrane where the tight junctions are located, in the
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Assignment 3 - Zachary Bergman Cell Bio 315 2/1/10 1. (1...

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