Polyphyllin I Induces Cell Cycle Arrest and Cell Apoptosis in Human Retinoblastoma Y-79 Cells through Targeting p53

2018 ◽  
Vol 18 (6) ◽  
pp. 875-881 ◽  
Author(s):  
Xue Zhu ◽  
Ke Wang ◽  
Kai Zhang ◽  
Yi Pan ◽  
Fanfan Zhou ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Cell Apoptosis ◽  
Potential Effect ◽  
External Beam Radiation ◽  
Beam Radiation ◽  
P53 Expression ◽  
Cycle Arrest ◽  
Wide Range ◽  
Human Retinoblastoma

Background: Retinoblastoma is the most common intraocular malignant tumor in childhood. Although external beam radiation and enucleation are effective to control retinoblastoma, eye salvage and vision preservation are still significant challenges. Polyphyllin I (PPI), a natural compound extracted from Paris polyphylla rhizomes, has a wide range of activities against many types of cancers. However, the potential effect of this herbal compound on retinoblastoma has not yet been investigated. Method: In the present study, we evaluated the cytotoxic effect of PPI on human retinoblastoma Y-79 cells as well as its underlying molecular mechanism. Our results indicated that PPI treatment significantly inhibited cell proliferation, arrested the cell cycle at G2/M phase and induced cell apoptosis of Y79 cells through the mitochondrial- dependent intrinsic pathway. Moreover, p53 is involved in PPI-induced cytotoxicity in human retinoblastoma Y-79 cells. Exposure to 10 μM PPI for 48 h dramatically induced the expression levels of p53, phosphorylated- p53 and acetylated-p53. Furthermore, blockade of p53 expression effectively attenuated PPI-induced cell cycle arrest and cell apoptosis in Y-79 cells. Result: These results demonstrated that PPI exhibits anti-proliferation effect on human retinoblastoma Y-79 cells through modulating p53 expression, stabilization and activation. This information shed light on the potential application of PPI in retinoblastoma therapy.

scholarly journals HIV-1 Vpr activates host CRL4-DCAF1 E3 ligase to degrade histone deacetylase SIRT7

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Xiaohong Zhou ◽  
Christina Monnie ◽  
Maria DeLucia ◽  
Jinwoo Ahn
Keyword(s):  
Cell Cycle ◽  
Dna Repair ◽  
Cell Cycle Arrest ◽  
Histone Deacetylase ◽  
E3 Ligase ◽  
Cycle Arrest ◽  
Wide Range ◽  
In Vitro Reconstitution ◽  
Hiv 1

Abstract Background Vpr is a virion-associated protein that is encoded by lentiviruses and serves to counteract intrinsic immunity factors that restrict infection. HIV-1 Vpr mediates proteasome-dependent degradation of several DNA repair/modification proteins. Mechanistically, Vpr directly recruits cellular targets onto DCAF1, a substrate receptor of Cullin 4 RING E3 ubiquitin ligase (CRL4) for poly-ubiquitination. Further, Vpr can mediate poly-ubiquitination of DCAF1-interacting proteins by the CRL4. Because Vpr-mediated degradation of its known targets can not explain the primary cell-cycle arrest phenotype that Vpr expression induces, we surveyed the literature for DNA-repair-associated proteins that interact with the CRL4-DCAF1. One such protein is SIRT7, a deacetylase of histone 3 that belongs to the Sirtuin family and regulates a wide range of cellular processes. We wondered whether Vpr can mediate degradation of SIRT7 via the CRL4-DCAF1. Methods HEK293T cells were transfected with cocktails of plasmids expressing DCAF1, DDB1, SIRT7 and Vpr. Ectopic and endogeneous levels of SIRT7 were monitered by immunoblotting and protein–protein interactions were assessed by immunoprecipitation. For in vitro reconstitution assays, recombinant CRL4-DCAF1-Vpr complexes and SIRT7 were prepared and poly-ubiqutination of SIRT7 was monitored with immunoblotting. Results We demonstrate SIRT7 polyubiquitination and degradation upon Vpr expression. Specifically, SIRT7 is shown to interact with the CRL4-DCAF1 complex, and expression of Vpr in HEK293T cells results in SIRT7 degradation, which is partially rescued by CRL inhibitor MNL4924 and proteasome inhibitor MG132. Further, in vitro reconstitution assays show that Vpr induces poly-ubiquitination of SIRT7 by the CRL4-DCAF1. Importantly, we find that Vpr from several different HIV-1 strains, but not HIV-2 strains, mediates SIRT7 poly-ubiquitination in the reconstitution assay and degradation in cells. Finally, we show that SIRT7 degradation by Vpr is independent of the known, distinctive phenotype of Vpr-induced cell cycle arrest at the G2 phase, Conclusions Targeting histone deacetylase SIRT7 for degradation is a conserved feature of HIV-1 Vpr. Altogether, our findings reveal that HIV-1 Vpr mediates down-regulation of SIRT7 by a mechanism that does not involve novel target recruitment to the CRL4-DCAF1 but instead involves regulation of the E3 ligase activity.

scholarly journals The RASSF6 Tumor Suppressor Protein Regulates Apoptosis and Cell Cycle Progression via Retinoblastoma Protein

2018 ◽  
Vol 38 (17) ◽  
Author(s):  
Shakhawoat Hossain ◽  
Hiroaki Iwasa ◽  
Aradhan Sarkar ◽  
Junichi Maruyama ◽  
Kyoko Arimoto-Matsuzaki ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Cell Cycle Arrest ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Loss Of Function ◽  
Cycle Progression ◽  
P53 Expression ◽  
Cycle Arrest ◽  
Hct116 Cells

ABSTRACT RASSF6 is a member of the tumor suppressor Ras association domain family (RASSF) proteins. RASSF6 is frequently suppressed in human cancers, and its low expression level is associated with poor prognosis. RASSF6 regulates cell cycle arrest and apoptosis and plays a tumor suppressor role. Mechanistically, RASSF6 blocks MDM2-mediated p53 degradation and enhances p53 expression. However, RASSF6 also induces cell cycle arrest and apoptosis in a p53-negative background, which implies that the tumor suppressor function of RASSF6 does not depend solely on p53. In this study, we revealed that RASSF6 mediates cell cycle arrest and apoptosis via pRb. RASSF6 enhances the interaction between pRb and protein phosphatase. RASSF6 also enhances P16INK4A and P14ARF expression by suppressing BMI1. In this way, RASSF6 increases unphosphorylated pRb and augments the interaction between pRb and E2F1. Moreover, RASSF6 induces TP73 target genes via pRb and E2F1 in a p53-negative background. Finally, we confirmed that RASSF6 depletion induces polyploid cells in p53-negative HCT116 cells. In conclusion, RASSF6 behaves as a tumor suppressor in cancers with loss of function of p53, and pRb is implicated in this function of RASSF6.

scholarly journals Propionate of a microbiota metabolite induces cell apoptosis and cell cycle arrest in lung cancer

2019 ◽  
Author(s):  
Kwangkho Kim ◽  
Ohman Kwon ◽  
Tae Ryu ◽  
Cho‑Rok Jung ◽  
Janghwan Kim ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Cell Apoptosis ◽  
Cycle Arrest

scholarly journals Eimeria tenella ROP kinase EtROP1 induces G0/G1 cell cycle arrest and inhibits host cell apoptosis

2019 ◽  
Vol 21 (7) ◽  
Author(s):  
Mamadou Amadou Diallo ◽  
Alix Sausset ◽  
Audrey Gnahoui‐David ◽  
Adeline Ribeiro E Silva ◽  
Aurélien Brionne ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Host Cell ◽  
Cell Apoptosis ◽  
Eimeria Tenella ◽  
Cycle Arrest ◽  
Host Cell Apoptosis ◽  
G1 Cell Cycle Arrest
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