Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy.
Dev Cell. 2013 Sep 16;26(5):483-95. doi: 10.1016/j.devcel.2013.07.013. Epub 2013 Aug 22.
Haspin is an atypical protein kinase that in several organisms phosphorylates histone H3Thr3 and is involved in chromosome segregation. In Saccharomyces cerevisiae, H3Thr3 phosphorylation has never been observed and the function of haspin is unknown. We show that deletion of ALK1 and ALK2 haspin paralogs causes the mislocalization of polarisome components. Following a transient mitotic arrest, this leads to an overly polarized actin distribution in the bud where the mitotic spindle is pulled. Here it elongates, generating anucleated mothers and binucleated daughters. Reducing the intensity of the bud-directed pulling forces partially restores proper cell division. We propose that haspin controls the localization of polarity cues to preserve the coordination between polarization and the cell cycle and to tolerate transient mitotic arrests. The evolutionary conservation of haspin and of the polarization mechanisms suggests that this function of haspin is likely shared with other eukaryotes, in which haspin may regulate asymmetric cell division.
Haspin 是一种非典型的蛋白激酶，在几种生物中，它可使组蛋白 H3Thr3 发生磷酸化，并参与染色体分离。在酿酒酵母中，从未观察到 H3Thr3 的磷酸化，且 haspin 的功能未知。我们发现，ALK1 和 ALK2 的缺失会导致极体成分的定位错误。短暂的有丝分裂停滞后，这会导致纺锤体被拉动的芽中 actin 分布过度极化。在这里，actin 延伸，产生无核母细胞和双核子细胞。减少芽定向拉力的强度部分恢复了正常的细胞分裂。我们提出，hspin 控制极性信号的定位，以保持极化和细胞周期之间的协调，并耐受短暂的有丝分裂停滞。hspin 和极化机制的进化保守性表明，hspin 的这一功能可能与其他真核生物共享，在这些生物中，hspin 可能调节不对称细胞分裂。
