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bioRxiv · 10.1101/169961

Tropomyosin and a-actinin cooperation inhibits fimbrin association with actin filament networks in fission yeast

Christensen, J.·Homa, K.·O'Connell, M.·Kovar, D. R.
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Abstract

We previously discovered that competition between fission yeast actin binding proteins (ABPs) for association with F-actin helps facilitate their sorting to different F-actin networks. Specifically, competition between actin patch ABPs fimbrin Fim1 and cofilin Adf1 enhances each others activities, and rapidly displaces tropomyosin Cdc8 from the F-actin network. However, these interactions dont explain how Fim1, a robust competitor, is prevented from associating equally well with other F-actin networks. Here, with a combination of fission yeast genetics, live cell fluorescent imaging, and in vitro TIRF microscopy, we identified the contractile ring ABP -actinin Ain1 as a key sorting factor. Fim1 competes with Ain1 for association with F-actin, which is dependent upon their residence time on F-actin. Remarkably, although Fim1 outcompetes both contractile ring ABPs Ain1 and Cdc8 individually, Cdc8 enhances the bundling activity of Ain1 10-fold, allowing the combination of Ain1 and Cdc8 to inhibit Fim1 association with contractile ring F-actin.

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Christensen, J., Homa, K., O'Connell, M., Kovar, D. R.. 2017-07-28. Tropomyosin and a-actinin cooperation inhibits fimbrin association with actin filament networks in fission yeast. https://doi.org/10.1101/169961

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