Title: In class activity: Microtubule Dynamism
Course: Biochemistry > Section: Week 2 - Unit 1_3: The Cytoskeleton

Purpose: To demonstrate the importance of dynamism of microtubules

Over to you:

A microtubule can oscillate between growing and shortening phases. This complex dynamic behavior allows the cell to quickly assemble or disassemble microtubule structures. Read the following questions from Alberts Bruce (Alberts, 2010) Essential cell biology and answer them.

Activity

Question 1:

The drug Taxol, extracted from the bark of yew trees, has an opposite effect to the drug colchicine, an alkaloid from autumn crocus. Taxol binds tightly to microtubules and stabilizes them; when added to cells, it causes much of the free tubulin to assemble into microtubules. In contrast, colchicine prevents microtubule formation. Taxol is just as pernicious to dividing cells as colchicine, and both are used as anticancer drugs. Based on your knowledge of microtubule dynamics, suggest why both drugs are toxic to dividing cells despite their opposite actions.

Question 2:

When cells enter mitosis, their existing array of cytoplasmic microtubules has to be rapidly broken down and replaced with the mitotic spindle that forms to pull the chromosomes into the daughter cells. The enzyme katanin, named after Japanese samurai swords, is activated during the onset of mitosis, and chops microtubules into short pieces.

What do you suppose is the fate of the microtubule fragments created by katanin? Explain your answer.