Rhind N, Furnari B, Russell P
Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Genes Dev. 1997 Feb 15;11(4):504-11. doi: 10.1101/gad.11.4.504.
A common cellular response to DNA damage is cell cycle arrest. This checkpoint control has been the subject of intensive genetic investigation, but the biochemical mechanism that prevents mitosis following DNA damage is unknown. In Schizosaccharomyces pombe, as well as vertebrates, the timing of mitosis under normal circumstances is determined by the balance of kinases and phosphatases that regulate inhibitory phosphorylation of Cdc2. In S. pombe, the phosphorylation occurs on tyrosine-15. This method of mitotic control is also used in S. pombe to couple mitosis with completion of DNA replication, but the role of Cdc2 tyrosine phosphorylation in the Chk1 kinase-mediated DNA damage checkpoint has remained uncertain. We show that, in contrast to recent speculation, the G2 DNA damage checkpoint arrest in S. pombe depends on the inhibitory tyrosine phosphorylation of Cdc2 carried out by the Wee1 and Mik1 kinases. Furthermore, the rate of Cdc2 tyrosine dephosphorylation is reduced by irradiation. This result implicates regulation of Cdc2 tyrosine dephosphorylation, mainly carried out by the Cdc25 tyrosine phosphatase, as an important part of the mechanism by which the DNA damage checkpoint induces Cdc2 inhibition and G2 arrest.
细胞对DNA损伤的一种常见反应是细胞周期停滞。这种关卡控制一直是深入遗传学研究的主题，但DNA损伤后阻止有丝分裂的生化机制尚不清楚。在粟酒裂殖酵母以及脊椎动物中，正常情况下有丝分裂的时间是由调节Cdc2抑制性磷酸化的激酶和磷酸酶的平衡决定的。在粟酒裂殖酵母中，磷酸化发生在酪氨酸-15上。这种有丝分裂控制方法在粟酒裂殖酵母中也用于将有丝分裂与DNA复制的完成联系起来，但Cdc2酪氨酸磷酸化在Chk1激酶介导的DNA损伤关卡中的作用仍不确定。我们发现，与最近的推测相反，粟酒裂殖酵母中的G2期DNA损伤关卡停滞取决于由Wee1和Mik1激酶进行的Cdc2抑制性酪氨酸磷酸化。此外，辐射会降低Cdc2酪氨酸去磷酸化的速率。这一结果表明，主要由Cdc25酪氨酸磷酸酶进行的Cdc2酪氨酸去磷酸化的调节，是DNA损伤关卡诱导Cdc2抑制和G2期停滞机制的重要组成部分。
