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1、.TitileSummaryDuring cell division, mitotic spindles are assembled by microtubule-based motorproteins1, 2. The bipolar organization of spindles is essential for proper segregation of chromosomes, and requires plus-end-directed homotetrameric motor proteins of thewidely conserved kinesin-5 (BimC) fam

2、ily3. Hypotheses for bipolar spindle formation include the 'push-pull mitotic muscle' model, in which kinesin-5 andopposing motor proteins act between overlapping microtubules2, 4, 5. However, the precise roles of kinesin-5 during this process are unknown. Here we show that the vertebrate ki

3、nesin-5 Eg5 drives the sliding of microtubules depending on their relativeorientation.We found in controlled in vitro assays that Eg5 has the remarkablecapability of simultaneously moving at20 nm s-1 towards the plus-ends of each ofthe two microtubules it crosslinks. For anti-parallel microtubules,

4、this results inrelative sliding at40 nm s-1, comparable to spindle pole separation rates in vivo6.Furthermore, we found that Eg5 can tether microtubule plus-ends, suggesting anadditional microtubule-binding mode for Eg5. Our results demonstrate how members of the kinesin-5 family are likely to funct

5、ion in mitosis, pushing apart interpolar microtubules as well as recruiting microtubules into bundles that are subsequently polarized by relative sliding. We anticipate our assay to be a starting point for more sophisticated in vitro models of mitotic spindles. For example, the individual and combin

6、ed action of multiple mitotic motors could be tested, including minus-end-directed motors opposing Eg5 motility. Furthermore, Eg5 inhibition is a major target of anti-cancer drug development, and a well-defined and quantitative assay for motor function will be relevant for such developments;.Content

7、Titile .1Summary.11Introduction .11.1Restatement of the Problem.11.2Background .11.1.1Common Solving Technique.11.1.2Previous Works .11.3Example .12Analysis of the Problem.12.1Outline of the Approach.12.2Basic Assumptions.22.3Definitions and Key Terms .23Calculating and Simplifying the Model .24The

8、Model Results.35Validating the Model.36Strengths and Weaknesses.36.1Strengths .36.2Weaknesses .37Food for Thought .38Conclusion .3References.4Appendices.4Appendix ASource Code.4Appendix B.4;.1 Introduction1.1 Restatement of the Problem1.2 Background1.3 Example2 Analysis of the Problem2.1 Outline of the Approach;.2.2 Basic Assumptions2.3 Definitions and Key TermsTable 1.SymbolMeaningUnit3 Calculating and Simplifying the Model;.4 The Model Results5 Validating the Model6 Strengths and Weaknesses6.1Strengths6.2Weaknesses7 Food for Thought8 Conclusion.;.ReferencesAppendi