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bioRxiv · 10.1101/554105

Temporal regulation of cell polarity via the interaction of the Ras GTPase Rsr1 and the scaffold protein Bem1

Miller, K. E.·Park, H.-O.
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Abstract

Establishing cell polarity is critical for growth and development of most organisms. The Cdc42 GTPase plays a central role in polarity development in species ranging from yeast to humans. In budding yeast, a specific growth site (i.e. bud site) is selected in the G1 phase, which determines the axis of cell polarization. Rsr1, a Ras GTPase, interacts with Cdc42 and its associated proteins to promote polarized growth at the proper bud site. Yet the mechanism underlying spatial cue-directed cell polarization is not fully understood. Here, we show that Rsr1 associates with Bem1, a scaffold protein, preferentially in its GDP-bound state in early G1. This interaction involves a part of the Bem1 Phox homology (PX) domain, which overlaps with a region previously shown to interact with Exo70, an exocyst component. Furthermore, overexpression of the constitutively GDP-bound Rsr1 interferes with Bem1s association with Exo70 and inhibits Bem1-dependent Exo70 polarization. We propose that Rsr1 plays a delicate role in coordination of spatial and temporal regulation of polarity establishment via its GTP- and GDP-bound states.

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Miller, K. E., Park, H.-O.. 2019-02-18. Temporal regulation of cell polarity via the interaction of the Ras GTPase Rsr1 and the scaffold protein Bem1. https://doi.org/10.1101/554105

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