The Department of Genetics, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
1] The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel [2] The Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 9112001, Israel.
Nat Commun. 2015 May 11;6:7075. doi: 10.1038/ncomms8075.
Ndd1 activates the Mcm1-Fkh2 transcription factor to transcribe mitotic regulators. The anaphase-promoting complex/cyclosome activated by Cdh1 (APC/C(Cdh1)) mediates the degradation of proteins throughout G1. Here we show that the APC/C(Cdh1) ubiquitinates Ndd1 and mediates its degradation, and that APC/C(Cdh1) activity suppresses accumulation of Ndd1 targets. We confirm putative Ndd1 targets and identify novel ones, many of them APC/C(Cdh1) substrates. The APC/C(Cdh1) thus regulates these proteins in a dual manner—both pretranscriptionally and post-translationally, forming a multi-layered feedforward loop (FFL). We predict by mathematical modelling and verify experimentally that this FFL introduces a lag between APC/C(Cdh1) inactivation at the end of G1 and accumulation of genes transcribed by Ndd1 in G2. This regulation generates two classes of APC/C(Cdh1) substrates, early ones that accumulate in S and late ones that accumulate in G2. Our results show how the dual state APC/C(Cdh1) activity is converted into multiple outputs by interactions between its substrates.
Ndd1 激活 Mcm1-Fkh2 转录因子来转录有丝分裂调节剂。由 Cdh1 激活的后期促进复合物/细胞周期蛋白（APC/C(Cdh1)) 介导 G1 期整个过程中蛋白质的降解。在这里，我们表明 APC/C(Cdh1) 泛素化 Ndd1 并介导其降解，并且 APC/C(Cdh1) 活性抑制 Ndd1 靶标的积累。我们确认了假定的 Ndd1 靶标并鉴定了新的靶标，其中许多是 APC/C(Cdh1) 的底物。因此，APC/C(Cdh1) 以双重方式调节这些蛋白质——既在转录前又在翻译后，形成一个多层次的前馈环 (FFL)。我们通过数学建模预测并通过实验验证，这个 FFL 在 G1 末期 APC/C(Cdh1) 失活和 Ndd1 在 G2 中转录的基因积累之间引入了一个滞后。这种调节产生了两类 APC/C(Cdh1) 底物，早期的在 S 期积累，晚期的在 G2 期积累。我们的结果表明，双态 APC/C(Cdh1) 活性如何通过其底物之间的相互作用转化为多个输出。
