Borgne A, Nurse P
Cell Cycle Laboratory, Imperial Cancer Research Found, Lincoln's Inn Fields, London, WC2A 3PX, UK.
J Cell Sci. 2000 Dec;113 Pt 23:4341-50. doi: 10.1242/jcs.113.23.4341.
Spd1p (for S phase delayed) is a cell cycle inhibitor in Schizosaccharomyces pombe. Spd1p overexpression blocks the onset of both S phase and mitosis. In this study, we have investigated the mechanisms by which Spd1p overexpression blocks cell cycle progression, focussing on the block over mitotic onset. High levels of Spd1p lead to an increase in Y15 phosphorylation of Cdc2p and we show that the block over G(2) requires the Wee1p kinase and is dependent on the rad and chk1/cds1 checkpoint genes. We propose that high levels of Spd1p in G(2) cells activate the DNA replication checkpoint control, which leads to a Wee1p-dependent increase of Cdc2p Y15 phosphorylation blocking onset of mitosis. The Spd1p block at S phase onset may act by interfering directly with DNA replication, and also activates the G(2 )rad/hus checkpoint pathway to block mitosis.
Spd1p（S期延迟蛋白）是粟酒裂殖酵母中的一种细胞周期抑制剂。Spd1p的过表达会阻断S期和有丝分裂的起始。在本研究中，我们研究了Spd1p过表达阻断细胞周期进程的机制，重点关注对有丝分裂起始的阻断。高水平的Spd1p会导致Cdc2p的Y15位点磷酸化增加，并且我们发现对G2期的阻断需要Wee1p激酶，且依赖于rad和chk1/cds1检查点基因。我们提出，G2期细胞中高水平的Spd1p会激活DNA复制检查点控制，这会导致Cdc2p的Y15位点磷酸化在Wee1p的作用下增加，从而阻断有丝分裂的起始。Spd1p在S期起始时的阻断可能通过直接干扰DNA复制起作用，并且还会激活G2期的rad/hus检查点途径来阻断有丝分裂。
