Myc stimulates cell cycle progression through the activation of Cdk1 and phosphorylation of p27

Abstract

Cell cycle stimulation is a major transforming mechanism of Myc oncoprotein. This is achieved through at least three concomitant mechanisms: upregulation of cyclins and Cdks, downregulation of the Cdk inhibitors p15 and p21 and the degradation of p27. The Myc-p27 antagonism has been shown to be relevant in human cancer. To be degraded, p27 must be phosphorylated at Thr-187 to be recognized by Skp2, a component of the ubiquitination complex. We previously described that Myc induces Skp2 expression. Here we show that not only Cdk2 but Cdk1 phosphorylates p27 at the Thr-187. Moreover, Myc induced p27 degradation in murine fibroblasts through Cdk1 activation, which was achieved by Myc-dependent cyclin A and B induction. In the absence of Cdk2, p27 phosphorylation at Thr-187 was mainly carried out by cyclin A2-Cdk1 and cyclin B1-Cdk1. We also show that Cdk1 inhibition was enough for the synthetic lethal interaction with Myc. This result is relevant because Cdk1 is the only Cdk strictly required for cell cycle and the reported synthetic lethal interaction between Cdk1 and Myc.

6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase Suppresses Neuronal Apoptosis by Increasing Glycolysis and “cyclin-dependent kinase 1-Mediated Phosphorylation of p27 After Traumatic Spinal Cord Injury in Rats

“…Consistent with previous studies, we found that the activation of PFKFB3 with meclizine significantly increased the level of nuclear PFKFB3 and CDK1. Moreover, consistent with a previous study 62 , our data demonstrated that increased nuclear CDK1 was accompanied by the enhanced phosphorylation of p27, as well as downregulated cellular apoptosis (evidenced by increased proportions of caspase-3-positive cells, TUNEL-positive cells, and abnormal ultrastructures). However, all of the antiapoptotic effects of meclizine against t-SCI were reversed by the CDK1 antagonist RO3306, suggesting a vital role of CDK1 in meclizine-mediated neuroprotective effects via modulating neuronal apoptosis.…”

A novel role of MNT as a negative regulator of REL and the NF-κB pathway

“…Quantitative polymerase chain reaction (qPCR) was performed with specific primers (Supplementary Table 2 ) using the iTaq™ Universal SYBR® Green Supermix (Bio-Rad) and CFX ConnectTM Real-Time PCR Detection System (Bio-Rad). RNA was converted into cDNA and analyzed as described 51 . Levels of mRNA were normalized against RPS14 (ribosomal protein S14) mRNA levels.…”

A novel role of MNT as a negative regulator of REL and the NF-κB pathway

“…Quantitative polymerase chain reaction (qPCR) was performed with specific primers ( Supplementary Table 2) using the iTaq™ Universal SYBR® Green Supermix (Bio-Rad) and CFX ConnectTM Real-Time PCR Detection System (Bio-Rad). RNA was converted into cDNA and analyzed as described 48 . Levels of mRNA were normalized against RPS14 mRNA levels.…”

“…For MNT-REL co-IP in LoVo cells, the cells were lysed instead with a mild hypotonic buffer (10 mM HEPES pH 7, 10 mM KCl, 0.25 mM EDTA pH 8, 0.125 mM EGTA pH 8, 0.5 mM spermidin, 0.1 % NP40, 1 mM DTT and phosphatase and protease inhibitors). Total cell lysis, immunoblots and immunoprecipitations (IPs) were performed as described 48 . The antibodies are shown in the Supplementary Table 3.…”

“…Nuclear extracts were obtained after a 5 min centrifugation at 1500 rpm and lysed with 1 % NP-40 IP lysis buffer (50 mM TrisHCl pH 7.5, 150 mM NaCl, 1 % NP-40, 1 mM EDTA pH 8, 0.5 mM EGTA pH 8 and protease and phosphatase inhibitors). Once the lysates were obtained, the immunoprecipitation and immunoblots were performed as described 48 .…”