Degradation of Ndd1 by APC/CCdh1 generates a feed forward loop that times mitotic protein accumulation

Abstract

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.

The Cell-Cycle Transcriptional Network Generates and Transmits a Pulse of Transcription Once Each Cell Cycle

“…Indeed, it has been shown that the activity of Hcm1 is regulated by CDK phosphorylation (Landry et al, 2014). On the other hand, Nrm1, Yhp1, and Ndd1 appear to be substrates of APC Cdh1 (Edenberg et al, 2015; Ostapenko and Solomon, 2011; Sajman et al, 2015), which is an E3 ubiquitin ligase complex normally inactivated at G1/S transition by CDK phosphorylation (Huang et al, 2001; Jaspersen et al, 1999; Yeong et al, 2001; Zachariae et al, 1998). If Cdh1 is normally inactivated by CDK at the G1/S border, then the cdc28-4 mutant cells should have constitutively active APC Cdh1 , and thus APC Cdh1 substrates might not accumulate at the protein level.…”

“…We excluded the cluster containing CDC20 that exhibited an early minor peak in the wild type datasets to avoid complex regulations by factors other than SFF. The remaining cluster contains 17 genes that partially overlapped with previously reported CLB2 cluster or SFF targets (Sajman et al, 2015; Spellman et al, 1998; Zhu et al, 2000).…”

Activation of the Anaphase Promoting Complex reverses multiple drug resistant cancer

“…The mRNAs encoding many APC substrates in yeast are also cell cycle regulated, with synthesis of their corresponding proteins peaking following the mRNA expression peak [75][76][77]. In fact, transcription factors that transcribe yeast APC substrates, such as Fkh1 [29] and Ndd1 [78], are targeted by the APC, thereby creating feedforward loops. This loop is further layered by the observation that the yeast Fkh2 transcription factor (also likely an APC target; our unpublished observation) recruits Ndd1 to chromatin of additional G2/M specific APC subunit promoters [79].…”

The cell-cycle transcriptional network generates and transmits a pulse of transcription once each cell cycle

“…We excluded the cluster containing CDC20 that exhibited an early minor peak in the wild type datasets to avoid complex regulations by factors other than SFF. The remaining cluster contains 17 genes that partially overlapped with previously reported CLB2 cluster or SFF targets [1,34,66].…”

“…Indeed, it has been shown that the activity of Hcm1 is regulated by CDK phosphorylation [31]. On the other hand, Nrm1, Yhp1, and Ndd1 appear to be substrates of APC Cdh1 [32][33][34], which is an E3 ubiquitin ligase complex normally inactivated at G1/S transition by CDK phosphorylation [35][36][37][38]. If Cdh1 is normally inactivated by CDK at the G1/S border, then the cdc28-4 mutant cells should have constitutively active APC Cdh1 , and thus APC Cdh1 substrates might not accumulate at the protein level.…”