TIF1 activates the intra-S-phase checkpoint response in the diploid micronucleus and amitotic polyploid macronucleus of Tetrahymena.
TIF1 activates the intra-S-phase checkpoint response in the diploid micronucleus and amitotic polyploid macronucleus of Tetrahymena.
复制标题
TIF1 激活四膜虫二倍体微核和无丝分裂多倍体大核中的 S 期内检查点反应。
DOI：
10.1091/mbc.e06-05-0469
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发表时间：
2006
影响因子：
3.3
通讯作者：
Kapler,GeoffreyM
中科院分区：
文献类型：
--
作者：
Yakisich,JSebastian;Sandoval,PamelaY;Morrison,TaraL;Kapler,GeoffreyM
核糖体DNA起源结合蛋白Tif1p调节rDNA复制的时间，是嗜热四膜虫S期正常进行和微核分裂所必需的。在这里，我们发现Tif1p在有丝分裂微核和无丝分裂大核中保护染色体免受DNA损伤。TIF1定位在各自的S时期移动到微核和大核中受到动态调节。TIF1突变株对羟基脲和甲基甲烷磺酸盐高度敏感，是DNA损伤的诱导者和S期内检查点停滞的诱导者。TIF1突变株在没有外源遗传毒性胁迫的情况下发生双链断裂，破坏所有五条微核染色体的稳定。野生型四膜虫引起S相内检查点反应，这种反应由羟基脲诱导，并被咖啡因抑制，咖啡因是顶端检查点激酶ATR/MEC1的抑制剂。相比之下，羟基脲诱导的TIF1突变体未能阻断在S期或咖啡因敏感的RAD51过表达，表明TIF1参与了检查点的激活。尽管TIF1突变体和咖啡因处理的野生型细胞发生了异常的微核和大核分裂，但TIF1p与ATR或其底物没有相似之处。我们认为TIF1和ATR在同一上位途径中调节二倍体有丝分裂微核和多倍体无丝分裂大核的检查点反应。
The ribosomal DNA origin binding protein Tif1p regulates the timing of rDNA replication and is required globally for proper S-phase progression and division of theTetrahymena thermophilamacronucleus. Here, we show that Tif1p safeguards chromosomes from DNA damage in the mitotic micronucleus and amitotic macronucleus.TIF1plocalization is dynamically regulated as it moves into the micro- and macronucleus during the respective S phases.TIF1disruption mutants are hypersensitive to hydroxyurea and methylmethanesulfonate, inducers of DNA damage and intra-S-phase checkpoint arrest in all examined eukaryotes.TIF1mutants incur double-strand breaks in the absence of exogenous genotoxic stress, destabilizing all five micronuclear chromosomes. Wild-typeTetrahymenaelicits an intra-S-phase checkpoint response that is induced by hydroxyurea and suppressed by caffeine, an inhibitor of the apical checkpoint kinaseATR/MEC1. In contrast, hydroxyurea-challengedTIF1mutants fail to arrest in S phase or exhibit caffeine-sensitive Rad51 overexpression, indicating the involvement ofTIF1in checkpoint activation. Although aberrant micro- and macronuclear division occurs inTIF1mutants and caffeine-treated wild-type cells,TIF1pbears no similarity toATRor its substrates. We propose thatTIF1andATRfunction in the same epistatic pathway to regulate checkpoint responses in the diploid mitotic micronucleus and polyploid amitotic macronucleus.