Many asymmetrically dividing cells unequally partition cellular structures according to age. Yet, it is unclear how cells differentiate pre-existing from newly synthesized material. Yeast cells segregate the spindle pole body (SPB, centrosome equivalent) inherited from the previous mitosis to the bud, while keeping the new one in the mother cell. Here, we show that the SPB inheritance network (SPIN), comprising the kinases Swe1 (also known as Wee1) and Kin3 (also known as Nek2) and the acetyltransferase NuA4 (also known as Tip60), distinguishes pre-existing from new SPBs. Swe1 phosphorylated Nud1 (orthologous to Centriolin) on young SPBs as they turned into pre-existing ones. The subsequent inactivation of Swe1 protected newly assembling SPBs from being marked. Kin3 and NuA4 maintained age marks on SPBs through following divisions. Downstream of SPIN, the Hippo regulator Bfa1–Bub2 bound the marked SPB, directed the spindle-positioning protein Kar9 towards it and drove its partition to the bud. Thus, coordination of SPIN activity and SPB assembly encodes age onto SPBs to enable their age-dependent segregation.

中文翻译：

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芽芽酵母Wee1区分纺锤极体，以指导其年龄依赖性分离的模式

许多不对称分裂的细胞根据年龄不平等地划分细胞结构。然而，目前尚不清楚细胞如何区分已有的和新合成的材料。酵母细胞隔离从先前的有丝分裂遗传到芽的纺锤极体（SPB，等价的中心体），同时将新的纺锤体保留在母细胞中。在这里，我们显示了包含激酶Swe1（也称为Wee1）和Kin3（也称为Nek2）和乙酰基转移酶NuA4（也称为Tip60）的SPB继承网络（SPIN）可以将新存在的SPB区分为已存在的SPB。Swe1将年轻的SPB上已存在的SPB磷酸化了Nud1（与Centriolin同源）。随后的Swe1灭活保护了新组装的SPB免受标记。Kin3和NuA4通过以下划分在SPB上保留了年龄标记。在SPIN的下游，河马调节子Bfa1–Bub2结合了标记的SPB，将纺锤定位蛋白Kar9引向它，并推动其向芽的分配。因此，SPIN活动和SPB装配的协调将年龄编码到SPB上，以实现它们的年龄依赖性隔离。