The fission yeast cells Schizosaccharomyces pombe divide at constant cell size regulated by environmental stimuli. An important pathway of cell size control involves the membrane-associated DYRK-family kinase Pom1, which forms decreasing concentration gradients from cell poles and inhibits mitotic inducers at mid-cell. Here, we identify the phosphatase 2C Ptc1 as negative regulator of Pom1. Ptc1 localizes to cell poles in a manner dependent on polarity and cell-wall integrity factors. We show that Ptc1 directly binds Pom1 and can dephosphorylate it in vitro but modulates Pom1 localization indirectly upon growth in low glucose conditions by influencing microtubule stability. Thus, Ptc1 phosphatase plays both direct and indirect roles in the Pom1 cell size control pathway.

裂殖酵母细胞粟酒裂殖酵母以受环境刺激调节的恒定细胞大小分裂。细胞大小控制的一个重要途径涉及与膜相关的 DYRK 家族激酶 Pom1，它从细胞极形成浓度梯度下降并抑制细胞中部的有丝分裂诱导物。在这里，我们将磷酸酶 2C Ptc1 鉴定为 Pom1 的负调节因子。Ptc1 以依赖于极性和细胞壁完整性因素的方式定位于细胞极点。我们表明 Ptc1 直接结合 Pom1 并可以在体外对其进行去磷酸化，但通过影响微管稳定性在低葡萄糖条件下间接调节 Pom1 定位。因此，Ptc1 磷酸酶在 Pom1 细胞大小控制途径中起着直接和间接的作用。