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Zhou L, Ng DSC, Yam JC, Chen LJ, Tham CC, Pang CP, Chu WK. Post-translational modifications on the retinoblastoma protein. J Biomed Sci 2022; 29:33. [PMID: 35650644 PMCID: PMC9161509 DOI: 10.1186/s12929-022-00818-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Accepted: 05/26/2022] [Indexed: 11/21/2022] Open
Abstract
The retinoblastoma protein (pRb) functions as a cell cycle regulator controlling G1 to S phase transition and plays critical roles in tumour suppression. It is frequently inactivated in various tumours. The functions of pRb are tightly regulated, where post-translational modifications (PTMs) play crucial roles, including phosphorylation, ubiquitination, SUMOylation, acetylation and methylation. Most PTMs on pRb are reversible and can be detected in non-cancerous cells, playing an important role in cell cycle regulation, cell survival and differentiation. Conversely, altered PTMs on pRb can give rise to anomalies in cell proliferation and tumourigenesis. In this review, we first summarize recent findings pertinent to how individual PTMs impinge on pRb functions. As many of these PTMs on pRb were published as individual articles, we also provide insights on the coordination, either collaborations and/or competitions, of the same or different types of PTMs on pRb. Having a better understanding of how pRb is post-translationally modulated should pave the way for developing novel and specific therapeutic strategies to treat various human diseases.
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Affiliation(s)
- Linbin Zhou
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Danny Siu-Chun Ng
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Jason C Yam
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
- Hong Kong Hub of Paediatric Excellence, The Chinese University of Hong Kong, Hong Kong, China
| | - Li Jia Chen
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
- Hong Kong Hub of Paediatric Excellence, The Chinese University of Hong Kong, Hong Kong, China
| | - Clement C Tham
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
- Hong Kong Hub of Paediatric Excellence, The Chinese University of Hong Kong, Hong Kong, China
| | - Chi Pui Pang
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
- Hong Kong Hub of Paediatric Excellence, The Chinese University of Hong Kong, Hong Kong, China
| | - Wai Kit Chu
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China.
- Hong Kong Hub of Paediatric Excellence, The Chinese University of Hong Kong, Hong Kong, China.
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong, China.
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2
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Thoma OM, Neurath MF, Waldner MJ. Cyclin-Dependent Kinase Inhibitors and Their Therapeutic Potential in Colorectal Cancer Treatment. Front Pharmacol 2021; 12:757120. [PMID: 35002699 PMCID: PMC8733931 DOI: 10.3389/fphar.2021.757120] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 11/26/2021] [Indexed: 12/17/2022] Open
Abstract
Cyclin-dependent kinases (CDKs) are key players in cell cycle regulation. So far, more than ten CDKs have been described. Their direct interaction with cyclins allow progression through G1 phase, transitions to S and G2 phase and finally through mitosis (M). While CDK activation is important in cell renewal, its aberrant expression can lead to the development of malignant tumor cells. Dysregulations in CDK pathways are often encountered in various types of cancer, including all gastrointestinal (GI) tract tumors. This prompted the development of CDK inhibitors as novel therapies for cancer. Currently, CDK inhibitors such as CDK4/6 inhibitors are used in pre-clinical studies for cancer treatment. In this review, we will focus on the therapeutic role of various CDK inhibitors in colorectal cancer, with a special focus on the CDK4/6 inhibitors.
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Affiliation(s)
- Oana-Maria Thoma
- Department of Medicine 1, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
- German Center for Immunotherapy (DZI), University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Markus F Neurath
- Department of Medicine 1, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
- German Center for Immunotherapy (DZI), University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Maximilian J Waldner
- Department of Medicine 1, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
- German Center for Immunotherapy (DZI), University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
- Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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3
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Hanaki S, Habara M, Masaki T, Maeda K, Sato Y, Nakanishi M, Shimada M. PP1 regulatory subunit NIPP1 regulates transcription of E2F1 target genes following DNA damage. Cancer Sci 2021; 112:2739-2752. [PMID: 33939241 PMCID: PMC8253265 DOI: 10.1111/cas.14924] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 04/14/2021] [Accepted: 04/14/2021] [Indexed: 12/21/2022] Open
Abstract
DNA damage induces transcriptional repression of E2F1 target genes and a reduction in histone H3‐Thr11 phosphorylation (H3‐pThr11) at E2F1 target gene promoters. Dephosphorylation of H3‐pThr11 is partly mediated by Chk1 kinase and protein phosphatase 1γ (PP1γ) phosphatase. Here, we isolated NIPP1 as a regulator of PP1γ‐mediated H3‐pThr11 by surveying nearly 200 PP1 interactor proteins. We found that NIPP1 inhibits PP1γ‐mediated dephosphorylation of H3‐pThr11 both in vivo and in vitro. By generating NIPP1‐depleted cells, we showed that NIPP1 is required for cell proliferation and the expression of E2F1 target genes. Upon DNA damage, activated protein kinase A (PKA) phosphorylated the NIPP1‐Ser199 residue, adjacent to the PP1 binding motif (RVxF), and triggered the dissociation of NIPP1 from PP1γ, leading to the activation of PP1γ. Furthermore, the inhibition of PKA activity led to the activation of E2F target genes. Statistical analysis confirmed that the expression of NIPP1 was positively correlated with E2F target genes. Taken together, these findings demonstrate that the PP1 regulatory subunit NIPP1 modulates E2F1 target genes by linking PKA and PP1γ during DNA damage.
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Affiliation(s)
- Shunsuke Hanaki
- Department of Biochemistry, Joint Faculty of Veterinary Science, Yamaguchi University, Yamaguchi, Japan
| | - Makoto Habara
- Department of Biochemistry, Joint Faculty of Veterinary Science, Yamaguchi University, Yamaguchi, Japan
| | - Takahiro Masaki
- Department of Biochemistry, Joint Faculty of Veterinary Science, Yamaguchi University, Yamaguchi, Japan
| | - Keisuke Maeda
- Department of Biochemistry, Joint Faculty of Veterinary Science, Yamaguchi University, Yamaguchi, Japan
| | - Yuki Sato
- Department of Biochemistry, Joint Faculty of Veterinary Science, Yamaguchi University, Yamaguchi, Japan
| | - Makoto Nakanishi
- Division of Cancer Biology, Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Midori Shimada
- Department of Biochemistry, Joint Faculty of Veterinary Science, Yamaguchi University, Yamaguchi, Japan
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4
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Fadraciclib (CYC065), a novel CDK inhibitor, targets key pro-survival and oncogenic pathways in cancer. PLoS One 2020; 15:e0234103. [PMID: 32645016 PMCID: PMC7347136 DOI: 10.1371/journal.pone.0234103] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Accepted: 05/19/2020] [Indexed: 01/12/2023] Open
Abstract
Cyclin-dependent kinases (CDKs) contribute to the cancer hallmarks of uncontrolled proliferation and increased survival. As a result, over the last two decades substantial efforts have been directed towards identification and development of pharmaceutical CDK inhibitors. Insights into the biological consequences of CDK inhibition in specific tumor types have led to the successful development of CDK4/6 inhibitors as treatments for certain types of breast cancer. More recently, a new generation of pharmaceutical inhibitors of CDK enzymes that regulate the transcription of key oncogenic and pro-survival proteins, including CDK9, have entered clinical development. Here, we provide the first disclosure of the chemical structure of fadraciclib (CYC065), a CDK inhibitor and clinical candidate designed by further optimization from the aminopurine scaffold of seliciclib. We describe its synthesis and mechanistic characterization. Fadraciclib exhibits improved potency and selectivity for CDK2 and CDK9 compared to seliciclib, and also displays high selectivity across the kinome. We show that the mechanism of action of fadraciclib is consistent with potent inhibition of CDK9-mediated transcription, decreasing levels of RNA polymerase II C-terminal domain serine 2 phosphorylation, the pro-survival protein Myeloid Cell Leukemia 1 (MCL1) and MYC oncoprotein, and inducing rapid apoptosis in cancer cells. This cellular potency and mechanism of action translate to promising anti-cancer activity in human leukemia mouse xenograft models. Studies of leukemia cell line sensitivity identify mixed lineage leukemia (MLL) gene status and the level of B-cell lymphoma 2 (BCL2) family proteins as potential markers for selection of patients with greater sensitivity to fadraciclib. We show that the combination of fadraciclib with BCL2 inhibitors, including venetoclax, is synergistic in leukemic cell models, as predicted from simultaneous inhibition of MCL1 and BCL2 pro-survival pathways. Fadraciclib preclinical pharmacology data support its therapeutic potential in CDK9- or CDK2-dependent cancers and as a rational combination with BCL2 inhibitors in hematological malignancies. Fadraciclib is currently in Phase 1 clinical studies in patients with advanced solid tumors (NCT02552953) and also in combination with venetoclax in patients with relapsed or refractory chronic lymphocytic leukemia (CLL) (NCT03739554) and relapsed refractory acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) (NCT04017546).
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5
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Upregulation of Phosphatase 1 Nuclear-Targeting Subunit (PNUTS) Is an Independent Predictor of Poor Prognosis in Prostate Cancer. DISEASE MARKERS 2020; 2020:7050146. [PMID: 32377272 PMCID: PMC7196962 DOI: 10.1155/2020/7050146] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 01/17/2020] [Indexed: 01/07/2023]
Abstract
Protein phosphatase 1 nuclear-targeting subunit (PNUTS) is ubiquitously expressed and associates with PTEN and protein phosphatase 1 (PP1) to control its activity. The role of PNUTS overexpression has hardly been studied in cancer. In this study, we used immunohistochemistry to quantitate PNUTS expression on a tissue microarray containing 17,747 clinical prostate cancer specimens. As compared to normal prostate epithelium, PNUTS expression was often higher in cancer. Among 12,235 interpretable tumors, PNUTS staining was negative in 21%, weak in 34%, moderate in 35%, and strong in 10% of cases. High PNUTS expression was associated with higher tumor stage, classical and quantitative Gleason grade, nodal stage, surgical margin, Ki67 labeling index, and early biochemical recurrence (p < 0.0001 each). PNUTS expression proved to be a moderate prognostic parameter with a maximal univariable Cox proportional hazard for PSA recurrence-free survival of 2.21 compared with 5.91 for Gleason grading. It was independent from established prognostic parameters in multivariable analysis. Comparison with molecular data available from earlier studies using the same TMA identified associations between high PNUTS expression and elevated androgen receptor expression (p < 0.0001), presence of TMPRSS2:ERG fusion (p < 0.0001), and 8 of 11 chromosomal deletions (3p13, 5q21, 8p21, 10q23, 12p13, 13q14, 16q24, and 17p13; p < 0.05 each). Particularly strong associations with PTEN and 12p13 deletions (p < 0.0001 each) may indicate a functional relationship, which has already been established for PNUTS and PTEN. PNUTS had no additional role on outcome in PTEN-deleted cancers. In conclusion, the results of our study identify high PNUTS protein levels as a predictor of poor prognosis possibly linked to increased levels of genomic instability. PNUTS measurement, either alone or in combination, might be of clinical utility in prostate cancers.
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6
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Fang Z, Lin M, Li C, Liu H, Gong C. A comprehensive review of the roles of E2F1 in colon cancer. Am J Cancer Res 2020; 10:757-768. [PMID: 32266089 PMCID: PMC7136928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 02/20/2020] [Indexed: 06/11/2023] Open
Abstract
E2F transcription factor 1 (E2F1) is a member of the E2F family of transcription factors. E2F1 binds to DNA with dimerization partner (DP) proteins through an E2 recognition site. The dissociation of E2F1 from retinoblastoma (Rb) protein recovers its transcriptional activity, which drives the cell cycle from the G1 to S phase. E2F1 has been shown to be involved in cellular proliferation, differentiation, and apoptosis in colon cancer. It was recently found that E2F1 also participates in the metastasis and chemoresistance of colon cancer. There are abundant experimental data regarding the actions of E2F1, which can be grouped as either pro-tumorigenic or pro-apoptotic. Despite a growing interest and plentiful data, there is currently no review that focuses on the role of E2F1 in colon cancer. Research on E2F1 and colon cancer has been scattered over various genes and microRNAs (miRNAs) that affect E2F1 expression. Here, we provide the first review that aims to consider and dissect all of the elucidated complex behaviors of E2F1 in colon cancer. This review also provides an analysis and conclusion regarding the current understanding of E2F1 in colon cancer in order to facilitate the direction of future research.
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Affiliation(s)
- Zejun Fang
- Central Laboratory, Sanmen People’s Hospital of Zhejiang, Sanmenwan Branch of The First Affiliated Hospital, College of Medicine, Zhejiang UniversitySanmen 317100, China
- Department of Gastroenterology, Sanmen People’s Hospital of Zhejiang, Sanmenwan Branch of The First Affiliated Hospital, College of Medicine, Zhejiang UniversitySanmen 317100, China
| | - Min Lin
- Central Laboratory, Sanmen People’s Hospital of Zhejiang, Sanmenwan Branch of The First Affiliated Hospital, College of Medicine, Zhejiang UniversitySanmen 317100, China
| | - Chunxiao Li
- Department of Gastroenterology, Ningbo First HospitalNingbo 315010, China
| | - Hong Liu
- Zhejiang Normal University-Jinhua People’s Hospital Joint Center for Biomedical ResearchJinhua 321004, China
- Department of Neuroscience, Center for Neurovirology, Lewis Katz School of Medicine at Temple UniversityPhiladelphia, PA 19140, USA
| | - Chaoju Gong
- Central Laboratory, The Municipal Affiliated Hospital of Xuzhou Medical UniversityXuzhou 221002, China
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7
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Thomas NA, Abraham RG, Dedi B, Krucher NA. Targeting retinoblastoma protein phosphorylation in combination with EGFR inhibition in pancreatic cancer cells. Int J Oncol 2018; 54:527-536. [PMID: 30535494 PMCID: PMC6317693 DOI: 10.3892/ijo.2018.4658] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 11/16/2018] [Indexed: 12/24/2022] Open
Abstract
Pancreatic ductal adenocarcinoma (PDAC) remains a particularly lethal disease that is resistant to targeted therapies. Tyrosine kinase inhibitors (TKIs), including erlotinib and gefitinib, which block the action of the human epidermal growth factor receptor type 1 receptor, provide small increases in patient survival when administered with gemcitabine. The retinoblastoma (Rb) tumor suppressor protein is an additional target in pancreatic cancer, due to its documented inactivation in PDAC. The present study, using cell number, apoptosis and immunoblotting assays, aimed to evaluate the effects of activation of the Rb tumor suppressor via dephosphorylation by small interfering RNA-mediated phosphatase activation. In the Panc1, MIAPaCa-2 and Capan-2 pancreatic cancer cell lines, and in normal H6c7 cells, the effects of phosphatase activation on Rb were revealed to be dependent on expression of the p16 tumor suppressor, which regulates Rb phosphorylation. Phosphatase activation had no effect on non-transformed pancreatic epithelial cells. When comparing kinase inhibition with phosphatase activation, it was demonstrated that kinase inhibition reduced proliferation, whereas phosphatase activation induced apoptosis. Both treatments together resulted in a greater reduction of pancreatic cancer cells than either treatment alone. In addition, the effects of combination treatment of phosphatase activation with TKIs on cell number and activation of the signal transducer and activator of transcription 3 (STAT3) resistance pathway were determined. The combination of Rb phosphatase activation with TKIs resulted in a greater reduction in cell number compared with either treatment alone, without STAT3 pathway activation. These data suggested that targeting Rb phosphorylation by activating phosphatase may be a rational strategy to inhibit pancreatic tumor cell growth, without activation of acquired resistance.
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Affiliation(s)
- Nimmi A Thomas
- Department of Biology, Pace University, Pleasantville, NY 10570, USA
| | - Rita G Abraham
- Department of Biology, Pace University, Pleasantville, NY 10570, USA
| | - Brixhilda Dedi
- Department of Biology, Pace University, Pleasantville, NY 10570, USA
| | - Nancy A Krucher
- Department of Biology, Pace University, Pleasantville, NY 10570, USA
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8
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Wang Z, Ma B, Li H, Xiao X, Zhou W, Liu F, Zhang B, Zhu M, Yang Q, Zeng Y, Sun Y, Sun S, Wang Y, Zhang Y, Weng H, Chen L, Ye M, An X, Liu J. Protein 4.1N acts as a potential tumor suppressor linking PP1 to JNK-c-Jun pathway regulation in NSCLC. Oncotarget 2016; 7:509-23. [PMID: 26575790 PMCID: PMC4808014 DOI: 10.18632/oncotarget.6312] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 11/02/2015] [Indexed: 12/15/2022] Open
Abstract
Protein 4.1N is a member of protein 4.1 family and has been recognized as a potential tumor suppressor in solid tumors. Here, we aimed to investigate the role and mechanisms of 4.1N in non-small cell lung cancer (NSCLC). We confirmed that the expression level of 4.1N was inversely correlated with the metastatic properties of NSCLC cell lines and histological grade of clinical NSCLC tissues. Specific knockdown of 4.1N promoted tumor cell proliferation, migration and adhesion in vitro, and tumor growth and metastasis in mouse xenograft models. Furthermore, we identified PP1 as a novel 4.1N-interacting molecule, and the FERM domain of 4.1N mediated the interaction between 4.1N and PP1. Further, ectopic expression of 4.1N could inactivate JNK-c-Jun signaling pathway through enhancing PP1 activity and interaction between PP1 and p-JNK. Correspondingly, expression of potential downstream metastasis targets (ezrin and MMP9) and cell cycle targets (p53, p21 and p19) of JNK-c-Jun pathway were also regulated by 4.1N. Our data suggest that down-regulation of 4.1N expression is a critical step for NSCLC development and that repression of JNK-c-Jun signaling through PP1 is one of the key anti-tumor mechanisms of 4.1N.
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Affiliation(s)
- Zi Wang
- The State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, China.,Department of Medicine, University of California, Irvine, CA, USA
| | - Bianyin Ma
- The State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, China
| | - Hui Li
- The State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, China
| | - Xiaojuan Xiao
- The State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, China
| | - Weihua Zhou
- The State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, China.,Department of Biochemistry, College of Medicine, Jishou University, Jishou, China
| | - Feng Liu
- Department of Medicine, University of California, Irvine, CA, USA
| | - Bin Zhang
- Department of Histology and Embryology, Xiangya School of Medicine, Central South University, Changsha, China
| | - Min Zhu
- The State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, China
| | - Qin Yang
- The State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, China
| | - Yayue Zeng
- The State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, China
| | - Yang Sun
- Molecular Science and Biomedicine Laboratory, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Collaborative Innovation Center for Chemistry and Molecular Medicine, Hunan University, Changsha, China
| | - Shuming Sun
- The State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, China
| | - Yanpeng Wang
- The State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, China
| | - Yibin Zhang
- The State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, China
| | - Haibo Weng
- College of Life Sciences, Zhengzhou University, Zhengzhou, China
| | - Lixiang Chen
- College of Life Sciences, Zhengzhou University, Zhengzhou, China
| | - Mao Ye
- Molecular Science and Biomedicine Laboratory, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Collaborative Innovation Center for Chemistry and Molecular Medicine, Hunan University, Changsha, China
| | - Xiuli An
- College of Life Sciences, Zhengzhou University, Zhengzhou, China.,Laboratory of Membrane Biology, New York Blood Center, New York, NY, USA
| | - Jing Liu
- The State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, China
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9
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Egger JV, Lane MV, Antonucci LA, Dedi B, Krucher NA. Dephosphorylation of the Retinoblastoma protein (Rb) inhibits cancer cell EMT via Zeb. Cancer Biol Ther 2016; 17:1197-1205. [PMID: 27645778 PMCID: PMC5137485 DOI: 10.1080/15384047.2016.1235668] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The tumor suppressor Retinoblastoma (Rb) protein is highly phosphorylated in cancer cells largely due to the overexpression of cyclins or the loss of expression of cyclin dependent kinase inhibitors (cdki). Hyperphosphorylation of Rb promotes proliferation, and plays a role in the regulation of apoptosis. Recently, inhibition of cyclin dependent activity toward Rb has been identified as a strategy that has shown clinical efficacy. We utilized a method to induce phosphatase activity toward Rb in cells by shRNA silencing of PNUTS (Phosphatase Nuclear Targeting Subunit) that regulates PP1-mediated dephosphorylation of Rb. In this study, the effect of Rb dephosphorylation on the epithelial to mesenchymal transition (EMT) was determined. The EMT transition is observed in cancer cells that have acquired invasive characteristics. In breast cancer cells grown in 3D Matrigel cultures, MCF7 cells undergo apoptosis in response to Rb dephosphorylation, whereas MDA-MB-231 and Hs578T cells exhibit a reduction in the EMT. Cells devoid of phosphorylated Rb (nontransformed MCF10A and Rb-null MDA-MB-468) lacked any response to PNUTS depletion, showing the effect is Rb-dependent. In addition, these studies showed that Rb dephosphorylation in 3D Matrigel cultures of highly invasive HT1080 cells led to the inhibition of the EMT. Furthermore we observed association between dephosphorylated Rb with ZEB1, a zinc-finger E-box-binding transcription factor that regulates expression of E- and N-cadherins. Finally Rb dephosphorylation led to inhibition of ZEB1 transcriptional activity, this data supports the notion that Rb dephosphorylation modulates the EMT. These studies suggest targeting Rb phosphorylation in mesenchymal cancer cells may decrease invasiveness.
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Affiliation(s)
- Jacklynn V Egger
- a Department of Biology , Dyson Hall, Pace University , Pleasantville , NY , USA
| | - Maria V Lane
- a Department of Biology , Dyson Hall, Pace University , Pleasantville , NY , USA
| | - Lisa A Antonucci
- a Department of Biology , Dyson Hall, Pace University , Pleasantville , NY , USA
| | - Brixhilda Dedi
- a Department of Biology , Dyson Hall, Pace University , Pleasantville , NY , USA
| | - Nancy A Krucher
- a Department of Biology , Dyson Hall, Pace University , Pleasantville , NY , USA
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10
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Antonucci LA, Egger JV, Krucher NA. Phosphorylation of the Retinoblastoma protein (Rb) on serine-807 is required for association with Bax. Cell Cycle 2015; 13:3611-7. [PMID: 25483096 PMCID: PMC4614104 DOI: 10.4161/15384101.2014.964093] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The recent finding that the Retinoblastoma protein (Rb) is able to regulate apoptosis in a non-transcriptional manner directly at the mitochondria by interaction with the pro-apoptotic protein Bax prompted this investigation of the complex formed between Rb and Bax. Because the function of Rb in the cellular processes of proliferation, apoptosis, senescence and differentiation is regulated by phosphorylation we endeavored to elucidate the phosphorylation status of Rb with respect to its association with Bax and its role in apoptosis. In this study we found that Rb phosphorylated on at least 4 C-terminal phosphorylation sites (S608, S795, S807/S811, and T821) is present at the mitochondria under non-stressed cellular conditions. An in vitro binding assay showed that Bax binds to Rb phosphorylated at S807/S811 in 3 cancer cell types. Physiologically relevant association between Bax and Rb phosphorylated on S807/S811 was demonstrated by reciprocal co-immunoprecipitation experiments using antibodies specific for Rb phosphorylated on S807/S811 and Bax. Mutant Rb proteins expressed in Rb-null C33A cells showed that phosphorylation of S807 of Rb promotes association with Bax and that mimicking phosphorylation at S807 of Rb can block the induction of apoptosis due to PNUTS downregulation. Finally using siRNA to activate phosphatase activity in MCF7 cells, Rb is dephosphorylated at several sites including S807/S811, dissociates from Bax and apoptosis is triggered. These studies show that phosphorylation of Rb regulates its association with Bax and its role in apoptosis.
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Affiliation(s)
- Lisa A Antonucci
- a Department of Biology and Health Science ; Pace University ; Pleasantville , NY USA
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11
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Ciurciu A, Duncalf L, Jonchere V, Lansdale N, Vasieva O, Glenday P, Rudenko A, Vissi E, Cobbe N, Alphey L, Bennett D. PNUTS/PP1 regulates RNAPII-mediated gene expression and is necessary for developmental growth. PLoS Genet 2013; 9:e1003885. [PMID: 24204300 PMCID: PMC3814315 DOI: 10.1371/journal.pgen.1003885] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 09/03/2013] [Indexed: 12/25/2022] Open
Abstract
In multicellular organisms, tight regulation of gene expression ensures appropriate tissue and organismal growth throughout development. Reversible phosphorylation of the RNA Polymerase II (RNAPII) C-terminal domain (CTD) is critical for the regulation of gene expression states, but how phosphorylation is actively modified in a developmental context remains poorly understood. Protein phosphatase 1 (PP1) is one of several enzymes that has been reported to dephosphorylate the RNAPII CTD. However, PP1's contribution to transcriptional regulation during animal development and the mechanisms by which its activity is targeted to RNAPII have not been fully elucidated. Here we show that the Drosophila orthologue of the PP1 Nuclear Targeting Subunit (dPNUTS) is essential for organismal development and is cell autonomously required for growth of developing tissues. The function of dPNUTS in tissue development depends on its binding to PP1, which we show is targeted by dPNUTS to RNAPII at many active sites of transcription on chromosomes. Loss of dPNUTS function or specific disruption of its ability to bind PP1 results in hyperphosphorylation of the RNAPII CTD in whole animal extracts and on chromosomes. Consistent with dPNUTS being a global transcriptional regulator, we find that loss of dPNUTS function affects the expression of the majority of genes in developing 1st instar larvae, including those that promote proliferative growth. Together, these findings shed light on the in vivo role of the PNUTS-PP1 holoenzyme and its contribution to the control of gene expression during early Drosophila development. During development, cells rely on appropriate patterns of gene expression to regulate metabolism in order to meet cellular demands and maintain rapid tissue growth. Conversely, dysregulation of gene expression is critical in various disease states, such as cancer, and during ageing. A key mechanism that is ubiquitously employed to control gene expression is reversible phosphorylation, a molecular switch that is used to regulate the activity of the transcriptional machinery. Here we identify an enzyme that binds to and regulates the phosphorylation state of RNA Polymerase II, a central component of the general transcription machinery. We also show that an essential role of this enzyme is to support normal patterns of gene expression that facilitate organismal growth. These findings are not only of relevance to the understanding of normal enzyme function but may also assist in the development of therapeutic strategies for the treatment of aberrant patterns of gene expression that occur during ageing and disease progression.
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Affiliation(s)
- Anita Ciurciu
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Louise Duncalf
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Vincent Jonchere
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Nick Lansdale
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Olga Vasieva
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Peter Glenday
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
- Department of Zoology, Oxford University, Oxford, United Kingdom
| | - Andreii Rudenko
- Department of Zoology, Oxford University, Oxford, United Kingdom
| | - Emese Vissi
- Department of Zoology, Oxford University, Oxford, United Kingdom
| | - Neville Cobbe
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Luke Alphey
- Department of Zoology, Oxford University, Oxford, United Kingdom
| | - Daimark Bennett
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
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