CYCLIN D1 AND CDK4 INDUCE HYPERTROPHY THROUGH PHOSPHORYLATION OF RNA POLYMERASE II C-TERMINAL DOMAIN IN NEONATAL RAT CARDIOMYOCYTES

We have previously reported that hypertrophic stimuli induce the expression of cyclinD1 and CDK4 in cardiomyocytes, and that overexpression of cyclin D1 and CDK4 causes hypertrophic change. Recently, it is reported that pTEFb (CDK9 and cyclinT) is involved in cardiac hypertrophy through phosphorylation of the RNA polymerase Ⅱ C-terminal domain (pol Ⅱ CTD), promoting transcript elongation by Pol Ⅱ. We assessed the hypothesis that cyclinD1/CDK4 induce hypertrophy through phosphorylation of pol Ⅱ CTD in cultured neonatal rat cardiomyocytes. In this study, we examined whether the overexpression of cyclinD1/CDK4 induces hypertrophy by using［3H］ leucine incorpolation assay. CyclinD1/CDK4 overexpression increased the rate of protein synthesis by 1.55 fold, compared to those in LacZ-overexpressed cells. Further, we assayed the rate of RNA synthesis by［3H］uridine incorpolation. Results showed that CyclinD1/CDK4 cells increased the rate of RNA synthesis compared to the control cells (1.57 fold).Finally, we examined whether phophorylation of pol Ⅱ CTD is involved in cyclinD1/CDK4-induced hypertrophy. DRB, a chemical antagonist of pol Ⅱ CTD phosphorylation, decreased the rate of incorporation of［3H］leucine and uridine in cyclinD1/CDK4 cells. These data altogether suggest that cyclinD1/CDK4 activates Pol Ⅱ transcription through inducing CTD phosphorylation and is involved in cardiac hypertrophy

ATF3 Protects against Renal Ischemia-Reperfusion Injury

Oxidative stress-induced cell death plays a major role in the progression of ischemic acute renal failure. Using microarrays, we sought to identify a stress-induced gene that may be a therapeutic candidate. Human proximal tubule (HK2) cells were treated with hydrogen peroxide (H2O2) and RNA was applied to an Affymetrix gene chip. Five genes were markedly induced in a parallel time-dependent manner by cluster analysis, including activating transcription factor 3 (ATF3), p21WAF1/CiP1 (p21), CHOP/GADD153, dual-specificity protein phosphatase, and heme oxygenase-1. H2O2 rapidly induced ATF3 approximately 12-fold in HK2 cells and approximately 6.5-fold in a mouse model of renal ischemia-reperfusion injury. Adenovirus-mediated expression of ATF3 protected HK2 cells against H2O2-induced cell death, and this was associated with a decrease of p53 mRNA and an increase of p21 mRNA. Moreover, when ATF3 was overexpressed in mice via adenovirus-mediated gene transfer, ischemia-reperfusion injury was reduced. In conclusion, ATF3 plays a protective role in renal ischemia-reperfusion injury and the mechanism of the protection may involve suppression of p53 and induction of p21

Phase I clinical study of oral olaparib in pediatric patients with refractory solid tumors: study protocol

Abstract Background There is no established standard chemotherapy for recurrent pediatric solid tumors such as neuroblastoma and sarcoma. Since some of these tumor cells show dysfunctions in homologous recombination repair, the goal is to conduct a phase I study of olaparib, a poly(ADP-ribose) polymerase inhibitor. In this clinical trial, the aims are to evaluate the safety, tolerability, and efficacy of olaparib in pediatric patients with refractory solid tumors and to recommend a dose for phase II trials. Methods In this open-label, multicenter study, olaparib tablets (62.5, 125, and 187.5 mg/m2 b.i.d.) will be administered orally in a standard 3 + 3 dose escalation design. Patients aged 3 to 18 years with recurrent pediatric solid tumors are eligible. Pharmacokinetic and pharmacodynamic analyses will also be performed. Discussion This study aims to extend the indications for olaparib by assessing its safety and efficacy in pediatric refractory solid tumor patients. Trial registration UMIN-CTR (UMIN000025521); Registered on January 4, 2017

Stress response gene ATF3 is a target of c-myc in serum-induced cell proliferation

The c-myc proto-oncogene encodes a transcription factor that promotes cell cycle progression and cell proliferation, and its deficiency results in severely retarded proliferation rates. The ATF3 stress response gene encodes a transcription factor that plays a role in determining cell fate under stress conditions. Its biological significance in the control of cell proliferation and its crosstalk regulation, however, are not well understood. Here, we report that the serum response of the ATF3 gene expression depends on c-myc gene and that the c-Myc complex at ATF/CREB site of the gene promoter plays a role in mediating the serum response. Intriguingly, ectopic expression of ATF3 promotes proliferation of c-myc-deficient cells, mostly by alleviating the impeded G1-phase progression observed in these cells, whereas ATF3 knockdown significantly suppresses proliferation of wild-type cells. Our study demonstrates that ATF3 is downstream of the c-Myc signaling pathway and plays a role in mediating the cell proliferation function of c-Myc. Our results provide a novel insight into the functional link of the stress response gene ATF3 and the proto-oncogene c-myc