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Luo Q, Di T, Chen Z, Peng J, Sun J, Xia Z, Pan W, Luo F, Lu F, Sun Y, Yang L, Zhang L, Miao‐Zhen Q, Yang D. A novel prognostic model predicts overall survival in colon cancer based on
RNA
splicing regulation gene expression. Cancer Sci 2022; 113:3330-3346. [PMID: 35792657 PMCID: PMC9530871 DOI: 10.1111/cas.15480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 06/14/2022] [Accepted: 06/21/2022] [Indexed: 11/30/2022] Open
Abstract
Colon cancer is the third most common cancer and the second leading cause of cancer‐related death worldwide. Dysregulated RNA splicing factors have been reported to be associated with tumorigenesis and development in colon cancer. In this study, we interrogated clinical and RNA expression data of colon cancer patients from The Cancer Genome Atlas (TCGA) dataset and the Gene Expression Omnibus (GEO) database. Genes regulating RNA splicing correlated with survival in colon cancer were identified and a risk score model was constructed using Cox regression analyses. In the risk model, RNA splicing factor peroxisome proliferator‐activated receptor‐γ coactivator‐1α (PPARGC1) is correlated with a good survival outcome, whereas Cdc2‐like kinase 1(CLK1), CLK2, and A‐kinase anchor protein 8‐like (AKAP8L) with a bad survival outcome. The risk model has a good performance for clinical prognostic prediction both in the TCGA cohort and the other two validation cohorts. In the tumor microenvironment (TME) analysis, the immune score was higher in the low‐risk group, and TME‐related pathway gene expression was also higher in low‐risk group. We further verified the mRNA and protein expression levels of these four genes in the adjacent nontumor, tumor, and liver metastasis tissues of colon cancer patients, which were consistent with bioinformatics analysis. In addition, knockdown of AKAP8L can suppress the proliferation and migration of colon cancer cells. Animal studies have also shown that AKAP8L knockdown can inhibit tumor growth in colon cancer in vivo. We established a prognostic risk model for colon cancer based on genes related to RNA splicing regulation and uncovered the role of AKAP8L in promoting colon cancer progression.
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Affiliation(s)
- Qiu‐Yun Luo
- The Eighth Affiliated Hospital, Sun Yat‐sen University 518033 Shenzhen China
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Experimental Research, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
| | - Tian Di
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Experimental Research, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
| | - Zhi‐Gang Chen
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Medical Oncology, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
| | - Jian‐Hong Peng
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Colorectal Surgery, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
| | - Jian Sun
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Clinical Research, The Third Affiliated Hospital 510060 Guangzhou China
| | - Zeng‐Fei Xia
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Experimental Research, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
| | - Wen‐Tao Pan
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Experimental Research, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
| | - Fan Luo
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Experimental Research, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
| | - Fei‐Teng Lu
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Experimental Research, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
| | - Yu‐Ting Sun
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Experimental Research, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
| | - Li‐Qiong Yang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Experimental Research, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
| | - Lin Zhang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Clinical Laboratory, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
| | - Qiu Miao‐Zhen
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Medical Oncology, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
| | - Da‐Jun Yang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat‐sen University Cancer Center 510060 Guangzhou China
- Department of Experimental Research, Sun Yat‐Sen University Cancer Center 510060 Guangzhou China
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Luo QY, Di T, Qiu MZ, Xia ZF, Du Y, Lin RD, Yang LQ, Sun YT, Yang DJ, Sun J, Zhang L. High AKAP8L expression predicts poor prognosis in esophageal squamous cell carcinoma. Cancer Cell Int 2022; 22:90. [PMID: 35189899 PMCID: PMC8862232 DOI: 10.1186/s12935-022-02492-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 01/27/2022] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Esophageal squamous cell carcinoma (ESCC) is a severe disease with high mortality, and is associated with poor prognosis and frequent lymphatic metastasis. Therefore, prognostic indicators for ESCC are urgently needed. A-kinase anchor-protein 8-like (AKAP8L) is a member of the A kinase anchor-protein (AKAPs) family and is overexpressed in many cancers. However, the role of AKAP8L in ESCC remains unclear. The aim of this study is to investigate the expression patterns and prognostic value of AKAP8L in ESCC. METHODS The mRNA expression of AKAP8L was analyzed from the dataset of The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO). Immunohistochemistry was applied to detect the AKAP8L expression in tissue microarray. Pearson's chi-square test was carried out for the correlation analysis of clinicopathological features and AKAP8L expression. The prognostic significance of clinicopathological features and AKAP8L expression was determined by univariate and multivariate Cox hazard models. Kaplan-Meier survival curve was used for survival analysis. RESULTS We found that the mRNA level of AKAP8L was higher in tumor tissues than in adjacent tissues in TCGA and GEO dataset. High AKAP8L expression was associated with poor overall survival (OS) in ESCC patients (p = 0.0039). Besides, AKAP8L expression was highly expressed in patients with lymph node metastasis detected by ESCC tissue microarray (p = 0.0014). The comparison of the different clinicopathological features of ESCC between high and low AKAP8L expression groups revealed that high AKAP8L expression was related to lymph node stage (p = 0.041). Kaplan-Meier survival analysis revealed that high AKAP8L expression indicates an unfavorable progression-free survival (PFS) and OS in ESCC patients (p < 0.0001). Univariate and multivariate analyses confirmed that AKAP8L was an independent prognostic factor for PFS and OS in ESCC (p = 0.003 and p < 0.0001). CONCLUSIONS In conclusion, this study demonstrated that high expression of AKAP8L is associated with poor prognosis of ESCC and can be considered an independent risk factor for ESCC.
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Affiliation(s)
- Qiu-Yun Luo
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China.,Department of Experimental Research, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China.,The Eighth Affiliated Hospital, Sun Yat-Sen University, Shenzhen, 518033, China
| | - Tian Di
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China.,Department of Experimental Research, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China
| | - Miao-Zhen Qiu
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China.,Department of Medical Oncology, Sun Yat-Sen University Cancer Center, Guangzhou, 510060, China
| | - Zeng-Fei Xia
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China.,Department of Experimental Research, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China
| | - Yong Du
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China.,Department of General Affairs Office, Sun Yat-Sen University Cancer Center, Guangzhou, 510060, China
| | - Run-Duan Lin
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China.,Department of Clinical Laboratory, Sun Yat-Sen University Cancer Center, Guangzhou, 510060, China
| | - Li-Qiong Yang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China.,Department of Experimental Research, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China
| | - Yu-Ting Sun
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China.,Department of Medical Oncology, Sun Yat-Sen University Cancer Center, Guangzhou, 510060, China
| | - Da-Jun Yang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China. .,Department of Experimental Research, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China.
| | - Jian Sun
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China. .,Department of Clinical Research, The Third Affiliated Hospital, Sun Yat-Sen University, Guangzhou, 510060, China.
| | - Lin Zhang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, P. R. China. .,Department of Clinical Laboratory, Sun Yat-Sen University Cancer Center, Guangzhou, 510060, China.
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3
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Melick CH, Meng D, Jewell JL. A-kinase anchoring protein 8L interacts with mTORC1 and promotes cell growth. J Biol Chem 2020; 295:8096-8105. [PMID: 32312749 DOI: 10.1074/jbc.ac120.012595] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 04/14/2020] [Indexed: 01/28/2023] Open
Abstract
mTOR complex 1 (mTORC1) senses nutrients to mediate anabolic processes within the cell. Exactly how mTORC1 promotes cell growth remains unclear. Here, we identified a novel mTORC1-interacting protein called protein kinase A anchoring protein 8L (AKAP8L). Using biochemical assays, we found that the N-terminal region of AKAP8L binds to mTORC1 in the cytoplasm. Importantly, loss of AKAP8L decreased mTORC1-mediated processes such as translation, cell growth, and cell proliferation. AKAPs anchor protein kinase A (PKA) through PKA regulatory subunits, and we show that AKAP8L can anchor PKA through regulatory subunit Iα. Reintroducing full-length AKAP8L into cells restored mTORC1-regulated processes, whereas reintroduction of AKAP8L missing the N-terminal region that confers the interaction with mTORC1 did not. Our results suggest a multifaceted role for AKAPs in the cell. We conclude that mTORC1 appears to regulate cell growth, perhaps in part through AKAP8L.
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Affiliation(s)
- Chase H Melick
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390.,Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390.,Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Delong Meng
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390.,Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390.,Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Jenna L Jewell
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390 .,Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390.,Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
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4
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Bieluszewska A, Weglewska M, Bieluszewski T, Lesniewicz K, Poreba E. PKA
‐binding domain of
AKAP
8 is essential for direct interaction with
DPY
30 protein. FEBS J 2018; 285:947-964. [DOI: 10.1111/febs.14378] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 12/01/2017] [Accepted: 12/22/2017] [Indexed: 11/27/2022]
Affiliation(s)
- Anna Bieluszewska
- Department of Molecular Virology Institute of Experimental Biology Faculty of Biology Adam Mickiewicz University in Poznan Poland
| | - Martyna Weglewska
- Department of Molecular Virology Institute of Experimental Biology Faculty of Biology Adam Mickiewicz University in Poznan Poland
| | - Tomasz Bieluszewski
- Department of Genome Biology Institute of Molecular Biology and Biotechnology Faculty of Biology Adam Mickiewicz University in Poznan Poland
| | - Krzysztof Lesniewicz
- Department of Molecular and Cellular Biology Institute of Molecular Biology and Biotechnology Faculty of Biology Adam Mickiewicz University in Poznan Poland
| | - Elzbieta Poreba
- Department of Molecular Virology Institute of Experimental Biology Faculty of Biology Adam Mickiewicz University in Poznan Poland
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5
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Søberg K, Skålhegg BS. The Molecular Basis for Specificity at the Level of the Protein Kinase a Catalytic Subunit. Front Endocrinol (Lausanne) 2018; 9:538. [PMID: 30258407 PMCID: PMC6143667 DOI: 10.3389/fendo.2018.00538] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 08/24/2018] [Indexed: 12/16/2022] Open
Abstract
Assembly of multi enzyme complexes at subcellular localizations by anchoring- and scaffolding proteins represents a pivotal mechanism for achieving spatiotemporal regulation of cellular signaling after hormone receptor targeting [for review, see (1)]. In the 3' 5'-cyclic adenosine monophosphate (cAMP) dependent protein kinase (PKA) signaling pathway it is generally accepted that specificity is secured at several levels. This includes at the first level stimulation of receptors coupled to heterotrimeric G proteins which through stimulation of adenylyl cyclase (AC) forms the second messenger cAMP. Cyclic AMP has several receptors including PKA. PKA is a tetrameric holoenzyme consisting of a regulatory (R) subunit dimer and two catalytic (C) subunits. The R subunit is the receptor for cAMP and compartmentalizes cAMP signals through binding to cell and tissue-specifically expressed A kinase anchoring proteins (AKAPs). The current dogma tells that in the presence of cAMP, PKA dissociates into an R subunit dimer and two C subunits which are free to phosphorylate relevant substrates in the cytosol and nucleus. The release of the C subunit has raised the question how specificity of the cAMP and PKA signaling pathway is maintained when the C subunit no longer is attached to the R subunit-AKAP complex. An increasing body of evidence points toward a regulatory role of the cAMP and PKA signaling pathway by targeting the C subunits to various C subunit binding proteins in the cytosol and nucleus. Moreover, recent identification of isoform specific amino acid sequences, motifs and three dimensional structures have together provided new insight into how PKA at the level of the C subunit may act in a highly isoform-specific fashion. Here we discuss recent understanding of specificity of the cAMP and PKA signaling pathway based on C subunit subcellular targeting as well as evolution of the C subunit structure that may contribute to the dynamic regulation of C subunit activity.
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Affiliation(s)
- Kristoffer Søberg
- Department of Medical Genetics, Oslo University Hospital, Oslo, Norway
| | - Bjørn Steen Skålhegg
- Section for Molecular Nutrition, University of Oslo, Oslo, Norway
- *Correspondence: Bjørn Steen Skålhegg
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6
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Marstad A, Landsverk OJB, Strømme O, Otterlei M, Collas P, Sundan A, Brede G. A-kinase anchoring protein AKAP95 is a novel regulator of ribosomal RNA synthesis. FEBS J 2016; 283:757-70. [PMID: 26683827 DOI: 10.1111/febs.13630] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 11/23/2015] [Accepted: 12/14/2015] [Indexed: 11/30/2022]
Abstract
The RNA polymerase I transcription apparatus acquires and integrates the combined information from multiple cellular signalling cascades to regulate ribosome production essential for cell growth and proliferation. In the present study, we show that a subpopulation of A-kinase anchoring protein 95 (AKAP95) targets the nucleolus during interphase and is involved in regulating rRNA production. We show that AKAP95 co-localizes with the nucleolar upstream binding factor, an essential rRNA transcription factor. Similar to other members of the C2 H2 -zinc finger family, we show, using systematic selection and evolution of ligands by exponential enrichment and in vitro binding analysis, that AKAP95 has a preference for GC-rich DNA in vitro, whereas fluorescence recovery after photobleaching analysis reveals AKAP95 to be a highly mobile protein that exhibits RNA polymerase I and II dependent nucleolar trafficking. In line with its GC-binding features, chromatin immunoprecipitation analysis revealed AKAP95 to be associated with ribosomal chromatin in vivo. Manipulation of AKAP95-expression in U2OS cells revealed a reciprocal relationship between the expression of AKAP95 and 47S rRNA. Taken together, our data indicate that AKAP95 is a novel nucleolus-associated protein with a regulatory role on rRNA production.
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Affiliation(s)
- Anne Marstad
- Centre of Molecular Inflammation Research (CEMIR), Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Ole Jørgen B Landsverk
- Department of Pathology, Centre for Immune Regulation, Oslo University Hospital Norway, Norway
| | - Olaf Strømme
- Centre of Molecular Inflammation Research (CEMIR), Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Marit Otterlei
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Philippe Collas
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Norway
| | - Anders Sundan
- Centre of Molecular Inflammation Research (CEMIR), Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.,KG Jebsen Centre for Myeloma Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| | - Gaute Brede
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
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7
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Xing L, Zhao X, Guo F, Kleiman L. The role of A-kinase anchoring protein 95-like protein in annealing of tRNALys3 to HIV-1 RNA. Retrovirology 2014; 11:58. [PMID: 25034436 PMCID: PMC4223510 DOI: 10.1186/1742-4690-11-58] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 07/07/2014] [Indexed: 12/04/2022] Open
Abstract
Background RNA helicase A (RHA), a DExH box protein, promotes annealing of tRNALys3, a primer for reverse transcription, to HIV-1 RNA and assembles into virus particles. A-kinase anchoring protein 95-like protein (HAP95) is a binding partner of RHA. The role of HAP95 in the annealing of tRNALys3 was examined in this study. Results HAP95 associates with the reverse transcriptase region of Pol protein of HIV-1. Decreasing endogenous HAP95 in HIV-1-producing 293T cells by siRNA reduces the amount of tRNALys3 annealed on viral RNA. This defect was further deteriorated by knockdown of RHA in the same cells, suggesting a cooperative effect between these two proteins. Biochemical assay in vitro using purified GST-tagged HAP95 shows that HAP95 may inhibit the activity of RHA. Conclusion The results support a hypothesis that HAP95 may transiently block RHA’s activity to protect the annealed tRNALys3 on viral RNA in the cells from removing by RHA during the packaging of RHA into virus particles, thus facilitating the annealing of tRNALys3 to HIV-1 RNA.
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Affiliation(s)
- Li Xing
- Lady Davis Institute for Medical Research and McGill AIDS Centre, Jewish General Hospital, Montreal, QC, Canada.
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8
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Abstract
The cell nucleus is responsible for the storage, expression, propagation, and maintenance of the genetic material it contains. Highly organized macromolecular complexes are required for these processes to occur faithfully in an extremely crowded nuclear environment. In addition to chromosome territories, the nucleus is characterized by the presence of nuclear substructures, such as the nuclear envelope, the nucleolus, and other nuclear bodies. Other smaller structural entities assemble on chromatin in response to required functions including RNA transcription, DNA replication, and DNA repair. Experiments in living cells over the last decade have revealed that many DNA binding proteins have very short residence times on chromatin. These observations have led to a model in which the assembly of nuclear macromolecular complexes is based on the transient binding of their components. While indeed most nuclear proteins are highly dynamic, we found after an extensive survey of the FRAP literature that an important subset of nuclear proteins shows either very slow turnover or complete immobility. These examples provide compelling evidence for the establishment of stable protein complexes in the nucleus over significant fractions of the cell cycle. Stable interactions in the nucleus may, therefore, contribute to the maintenance of genome integrity. Based on our compilation of FRAP data, we propose an extension of the existing model for nuclear organization which now incorporates stable interactions. Our new “induced stability” model suggests that self-organization, self-assembly, and assisted assembly contribute to nuclear architecture and function.
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9
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Portal D, Zhao B, Calderwood MA, Sommermann T, Johannsen E, Kieff E. EBV nuclear antigen EBNALP dismisses transcription repressors NCoR and RBPJ from enhancers and EBNA2 increases NCoR-deficient RBPJ DNA binding. Proc Natl Acad Sci U S A 2011; 108:7808-13. [PMID: 21518914 DOI: 10.1073/pnas.1104991108] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
EBV nuclear antigen 2 (EBNA2) and EBV nuclear antigen LP (EBNALP) are critical for B-lymphocyte transformation to lymphoblastoid cell lines (LCLs). EBNA2 activates transcription through recombination signal-binding immunoglobulin κJ region (RBPJ), a transcription factor associated with NCoR repressive complexes, and EBNALP is implicated in repressor relocalization. EBNALP coactivation with EBNA2 was found to dominate over NCoR repression. EBNALP associated with NCoR and dismissed NCoR, NCoR and RBPJ, or NCoR, RBPJ, and EBNA2 from matrix-associated deacetylase (MAD) bodies. In non-EBV-infected BJAB B lymphoma cells that stably express EBNA2, EBNALP, or EBNA2 and EBNALP, EBNALP was associated with hairy and enhancer of split 1 (hes1), cd21, cd23, and arginine and glutamate-rich 1 (arglu1) enhancer or promoter DNA and was associated minimally with coding DNA. With the exception of RBPJ at the arglu1 enhancer, NCoR and RBPJ were significantly decreased at enhancer and promoter sites in EBNALP or EBNA2 and EBNALP BJAB cells. EBNA2 DNA association was unaffected by EBNALP, and EBNALP was unaffected by EBNA2. EBNA2 markedly increased RBPJ at enhancer sites without increasing NCoR. EBNALP further increased hes1 and arglu1 RNA levels with EBNA2 but did not further increase cd21 or cd23 RNA levels. EBNALP in which the 45 C-terminal residues critical for transformation and transcriptional activation were deleted associated with NCoR but was deficient in dismissing NCoR from MAD bodies and from enhancer and promoter sites. These data strongly support a model in which EBNA2 association with NCoR-deficient RBPJ enhances transcription and EBNALP dismisses NCoR and RBPJ repressive complexes from enhancers to coactivate hes1 and arglu1 but not cd21 or cd23.
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10
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Kvissel AK, Ørstavik S, Eikvar S, Brede G, Jahnsen T, Collas P, Akusjärvi G, Skålhegg BS. Involvement of the catalytic subunit of protein kinase A and of HA95 in pre-mRNA splicing. Exp Cell Res 2007; 313:2795-809. [PMID: 17594903 DOI: 10.1016/j.yexcr.2007.05.014] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2006] [Revised: 03/31/2007] [Accepted: 05/01/2007] [Indexed: 11/30/2022]
Abstract
Protein kinase A (PKA) is a holoenzyme consisting of two catalytic (C) subunits bound to a regulatory (R) subunit dimer. Stimulation by cAMP dissociates the holoenzyme and causes translocation to the nucleus of a fraction of the C subunit. Apart from transcription regulation, little is known about the function of the C subunit in the nucleus. In the present report, we show that both Calpha and Cbeta are localized to spots in the mammalian nucleus. Double immunofluorescence analysis of splicing factor SC35 with the C subunit indicated that these spots are splicing factor compartments (SFCs). Using the E1A in vivo splicing assay, we found that catalytically active C subunits regulate alternative splicing and phosphorylate several members of the SR-protein family of splicing factors in vitro. Furthermore, nuclear C subunits co-localize with the C subunit-binding protein homologous to AKAP95, HA95. HA95 also regulates E1A alternative splicing in vivo, apparently through its N-terminal domain. Localization of the C subunit to SFCs and the E1A splicing pattern were unaffected by cAMP stimulation. Our findings demonstrate that the nuclear PKA C subunit co-locates with HA95 in SFCs and regulates pre-mRNA splicing, possibly through a cAMP-independent mechanism.
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11
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Li Y, Kao GD, Garcia BA, Shabanowitz J, Hunt DF, Qin J, Phelan C, Lazar MA. A novel histone deacetylase pathway regulates mitosis by modulating Aurora B kinase activity. Genes Dev 2006; 20:2566-79. [PMID: 16980585 PMCID: PMC1578679 DOI: 10.1101/gad.1455006] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Histone deacetylase (HDAC) inhibitors perturb the cell cycle and have great potential as anti-cancer agents, but their mechanism of action is not well established. HDACs classically function as repressors of gene expression, tethered to sequence-specific transcription factors. Here we report that HDAC3 is a critical, transcription-independent regulator of mitosis. HDAC3 forms a complex with A-Kinase-Anchoring Proteins AKAP95 and HA95, which are targeted to mitotic chromosomes. Deacetylation of H3 in mitosis requires AKAP95/HA95 and HDAC3 and provides a hypoacetylated H3 tail that is the preferred substrate for Aurora B kinase. Phosphorylation of H3S10 by Aurora B leads to dissociation of HP1 proteins from methylated H3K9 residues on mitotic heterochromatin. This transcription-independent pathway, involving interdependent changes in histone modification and protein association, is required for normal progression through mitosis and is an unexpected target of HDAC inhibitors, a class of drugs currently in clinical trials for treating cancer.
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Affiliation(s)
- Yun Li
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, Institute for Diabetes, Obesity, and Metabolism, University of Pennsylvania School of Medicine, Philadelphia, 19104, USA
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12
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Yang Y, Mahaffey CL, Bérubé N, Frankel WN. Interaction between fidgetin and protein kinase A-anchoring protein AKAP95 is critical for palatogenesis in the mouse. J Biol Chem 2006; 281:22352-22359. [PMID: 16751186 DOI: 10.1074/jbc.m603626200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The gene defective in fidget mice encodes fidgetin, a member of the AAA (ATPases associated with diverse cellular activities) family of ATPases. Using a yeast two-hybrid screen, we identified cAMP-dependent protein kinase A anchoring protein 95 kDa (AKAP95) as a potential fidgetin-binding protein. Epitope-tagged fidgetin co-localized with endogenous AKAP95 in the nuclear matrix, and the physical interaction between fidgetin and AKAP95 was further confirmed by reciprocal immunoprecipitation. To evaluate the biological significance of the fidgetin-AKAP95 binding, we created AKAP95 mutant mice through a gene trap strategy. Akap95 mutant mice are surprisingly viable with no overt phenotype. However, a significant number of mice carrying both Akap95 and fidget mutations die soon after birth due to cleft palate, consistent with the overlapping expression of AKAP95 and fidgetin in the branchial arches during mouse embryogenesis. These results expand the spectrum of the pleiotropic phenotypes of fidget mice and provide new leads on the in vivo function of AKAP95.
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Affiliation(s)
- Yan Yang
- Jackson Laboratory, Bar Harbor, Maine 04609
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13
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Sayer JA, Manczak M, Akileswaran L, Reddy PH, Coghlan VM. Interaction of the nuclear matrix protein NAKAP with HypA and huntingtin: implications for nuclear toxicity in Huntington's disease pathogenesis. Neuromolecular Med 2006; 7:297-310. [PMID: 16391387 DOI: 10.1385/nmm:7:4:297] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2005] [Revised: 07/05/2005] [Accepted: 07/08/2005] [Indexed: 11/11/2022]
Abstract
Although expansion of a polyglutamine tract in the huntingtin protein is known to cause Huntington's disease (HD), there is considerable debate as to how this mutation leads to the selective neuronal loss that characterizes the disease. The observation that mutant huntingtin accumulates in neuronal nuclei has led to the hypothesis that the molecular mechanism may involve the disruption of specific nuclear activities. Recently, several nuclear interaction partners for huntingtin have been identified, including HypA, a splicing factor-like protein of unknown function. Using a yeast two-hybrid screen, we have identified the interaction of HypA with the nuclear scaffold protein NAKAP. Interaction of NAKAP with HypA is specific and occurs both in yeast and in vitro. Deletion-mapping studies indicate that binding occurs via a proline-rich domain in NAKAP with a WW domain of HypA. In cultured cells, NAKAP and HypA localize within the nucleus and copurify with the nuclear matrix. Furthermore, NAKAP associates with HypA from human brain and copurifies with huntingtin protein in brain tissue obtained from HD patients. In HD neurons, NAKAP and mutant huntingtin were colocalized to the nuclear matrix and were found to be components of nuclear aggregates. Hence, the NAKAP-HypA scaffold is a potential nuclear docking site for huntingtin protein and may contribute to the nuclear accumulation of huntingtin observed in HD.
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Affiliation(s)
- Jonathan A Sayer
- Neurological Sciences Institute, Oregon Health & Science University, Beaverton, OR 97006, USA
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14
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Abstract
The nuclear envelope mediates key functions by interacting with chromatin. We recently reported an interaction between the chromatin- and nuclear matrix-associated protein HA95 and the inner nuclear membrane integral protein LAP2beta, implicated in initiation of DNA replication (Martins et al. (2003) J. Cell Biol. 160, 177-188). Here, we show that in vitro, interaction between HA95 and LAP2beta is modulated by cAMP signaling via PKA. Exposure of an anti-HA95 immune precipitate from interphase HeLa cells to a mitotic extract promotes ATP-dependent release of LAP2beta from the HA95 complex. This coincides with Ser and Thr phosphorylation of HA95 and LAP2beta. Inhibition of PKA with PKI abolishes phosphorylation of HA95 and dissociation of LAP2beta from HA95, although LAPbeta remains phosphorylated. Antagonizing cAMP signaling in mitotic extract also abolishes the release of LAP2beta from HA95; however, disrupting PKA anchoring to A-kinase anchoring proteins has no effect. Inhibition of CDK activity in the extract greatly reduces LAP2beta phosphorylation but does not prevent LAP2beta release from HA95. Inhibition of PKC, MAP kinase, or CaM kinase II does not affect mitotic extract-induced dissociation of LAP2beta from HA95. PKA phosphorylates HA95 but not LAP2beta in vitro and elicits a release of LAP2beta from HA95. CDK1 or PKC phosphorylates LAP2beta within the HA95 complex, but neither kinase induces LAP2beta release. Our results indicate that in vitro, the interaction between HA95 and LAP2beta is influenced by a PKA-mediated phosphorylation of HA95 rather than by CDK1- or PKC-mediated phosphorylation of LAP2beta. This suggests an additional level of regulation of a chromatin-nuclear envelope interaction in dividing cells.
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Affiliation(s)
- Sandra B Martins
- Institute of Medical Biochemistry, University of Oslo, P.O. Box 1112 Blindern, 0317 Oslo, Norway
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Eide T, Taskén KA, Carlson C, Williams G, Jahnsen T, Taskén K, Collas P. Protein kinase A-anchoring protein AKAP95 interacts with MCM2, a regulator of DNA replication. J Biol Chem 2003; 278:26750-6. [PMID: 12740381 DOI: 10.1074/jbc.m300765200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein kinase A (PKA)-anchoring protein AKAP95 is localized to the nucleus in interphase, where it primarily associates with the nuclear matrix. A yeast two-hybrid screen for AKAP95 interaction partners identified the minichromosome maintenance (MCM) 2 protein, a component of the pre-replication complex. AKAP95-MCM2 interaction was mapped to residues 1-195 of AKAP95 and corroborated by glutathione S-transferase precipitation and immunoprecipitation from chromatin. Disruption of AKAP95-MCM2 interaction with an AKAP95-(1-195) peptide within HeLa cell nuclei abolishes initiation of DNA replication in G1 phase and the elongation phase of replication in vitro without affecting global nuclear organization or import. Disruption of the C-terminal zinc finger of AKAP95 reduces efficiency of replication initiation. Disruption of the PKA-binding domain does not impair replication in G1- or S-phase nuclei, whereas a PKA inhibitor affects the initiation but not the elongation phase of replication. Depleting AKAP95 from nuclei partially depletes MCM2 and abolishes replication. Recombinant AKAP95 restores intranuclear MCM2 and replication in a dose-dependent manner. Our results suggest a role of AKAP95 in DNA replication by providing a scaffold for MCM2.
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Affiliation(s)
- Turid Eide
- Department of Medical Biochemistry, University of Oslo, P. O. Box 1112 Blindern, 0317 Oslo, Norway
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16
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Martins S, Eikvar S, Furukawa K, Collas P. HA95 and LAP2 beta mediate a novel chromatin-nuclear envelope interaction implicated in initiation of DNA replication. J Cell Biol 2003; 160:177-88. [PMID: 12538639 PMCID: PMC2172640 DOI: 10.1083/jcb.200210026] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
HA95 is a chromatin-associated protein that interfaces the nuclear envelope (NE) and chromatin. We report an interaction between HA95 and the inner nuclear membrane protein lamina-associated polypeptide (LAP) 2 beta, and a role of this association in initiation of DNA replication. Precipitation of GST-LAP2 beta fusion proteins and overlays of immobilized HA95 indicate that a first HA95-binding region lies within amino acids 137-242 of LAP2 beta. A second domain sufficient to bind HA95 colocalizes with the lamin B-binding domain of LAP2beta at residues 299-373. HA95-LAP2 beta interaction is not required for NE formation. However, disruption of the association of HA95 with the NH2-terminal HA95-binding domain of LAP2 beta abolishes the initiation, but not elongation, of DNA replication in purified G1 phase nuclei incubated in S-phase extract. Inhibition of replication initiation correlates with proteasome-mediated proteolysis of Cdc6, a component of the prereplication complex. Rescue of Cdc6 degradation with proteasome inhibitors restores replication. We propose that an interaction of LAP2beta, or LAP2 proteins, with HA95 is involved in the control of initiation of DNA replication.
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Affiliation(s)
- Sandra Martins
- Institute of Medical Biochemistry, University of Oslo, Oslo 0317, Norway
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Han I, Xue Y, Harada S, Orstavik S, Skalhegg B, Kieff E. Protein kinase A associates with HA95 and affects transcriptional coactivation by Epstein-Barr virus nuclear proteins. Mol Cell Biol 2002; 22:2136-46. [PMID: 11884601 PMCID: PMC133669 DOI: 10.1128/mcb.22.7.2136-2146.2002] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
HA95, a nuclear protein homologous to AKAP95, has been identified in immune precipitates of the Epstein-Barr virus (EBV) coactivating nuclear protein EBNA-LP from EBV-transformed lymphoblastoid cells (LCLs). We now find that HA95 and EBNA-LP are highly associated in LCLs and in B-lymphoma cells where EBNA-LP is expressed by gene transfer. Binding was also evident in yeast two-hybrid assays. HA95 binds to the EBNA-LP repeat domain that is the principal coactivator of transcription. EBNA-LP localizes with HA95 and causes HA95 to partially relocalize with EBNA-LP in promyelocytic leukemia nuclear bodies. Protein kinase A catalytic subunit alpha (PKAcsalpha) is significantly associated with HA95 in the presence or absence of EBNA-LP. Although EBNA-LP is not a PKA substrate, HA95 or PKAcsalpha expression in B lymphoblasts specifically down-regulates the strong coactivating effects of EBNA-LP. The inhibitory effects of PKAcsalpha are reversed by coexpression of protein kinase inhibitor. PKAcsalpha also inhibits EBNA-LP coactivation with the EBNA-2 acidic domain fused to the Gal4 DNA binding domain. Furthermore, EBNA-LP- and EBNA-2-induced expression of the EBV oncogene, LMP1, is down-regulated by PKAcsalpha or HA95 expression in EBV-infected lymphoblasts. These experiments indicate that HA95 and EBNA-LP localize PKAcsalpha at nuclear sites where it can affect transcription from specific promoters. The role of HA95 as a scaffold for transcriptional regulation is discussed.
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Affiliation(s)
- Innoc Han
- Ewha Institute of Neuroscience, Ewha University Medical School, Seoul 110-783, Korea
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Affiliation(s)
- S D Georgatos
- Department of Basic Sciences, The University of Crete, School of Medicine, Stavrakia, 71 110 Heraklion, Crete, Greece.
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19
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Abstract
cAMP-dependent protein kinase is targeted to discrete subcellular locations by a family of specific anchor proteins (A-kinase anchor proteins, AKAPs). Localization recruits protein kinase A (PKA) holoenzyme close to its substrate/effector proteins, directing and amplifying the biological effects of cAMP signaling.AKAPs include two conserved structural modules: (i) a targeting domain that serves as a scaffold and membrane anchor; and (ii) a tethering domain that interacts with PKA regulatory subunits. Alternative splicing can shuffle targeting and tethering domains to generate a variety of AKAPs with different targeting specificity. Although AKAPs have been identified on the basis of their interaction with PKA, they also bind other signaling molecules, mainly phosphatases and kinases, that regulate AKAP targeting and activate other signal transduction pathways. We suggest that AKAP forms a "transduceosome" by acting as an autonomous multivalent scaffold that assembles and integrates signals derived from multiple pathways. The transduceosome amplifies cAMP and other signals locally and, by stabilizing and reducing the basal activity of PKA, it also exerts long-distance effects. The AKAP transduceosome thus optimizes the amplitude and the signal/noise ratio of cAMP-PKA stimuli travelling from the membrane to the nucleus and other subcellular compartments.
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Affiliation(s)
- A Feliciello
- Dipartimento di Biologia, Centro di Endocrinologia ed Oncologia Sperimentale CNR, Facoltá di Medicina, via S. Pansini, 5, Universitá Federico II, 80131, Napoli, Italy.
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20
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Abstract
EBNA-LP-associated proteins were identified by sequencing proteins that immunoprecipitated with Flag epitope-tagged EBNA-LP (FLP) from lymphoblasts in which FLP was stably expressed. The association of EBNA-LP with Hsp70 (72/73) was confirmed, and sequences of DNA-PK catalytic subunit (DNA-PKcs), HA95, Hsp27, prolyl 4-hydroxylase alpha-1 subunit, alpha-tubulin, and beta-tubulin were identified. The fraction of total cellular HA95 that associated with FLP was very high, while progressively lower fractions of the total DNA-PKcs, Hsp70, Hsp 27, alpha-tubulin, and beta-tubulin specifically associated with EBNA-LP as determined by immunoblotting with antibodies to these proteins. EBNA-LP bound to two domains in the DNA-PKcs C terminus and DNA-PKcs associated with the EBNA-LP repeat domain. DNA-PKcs that was bound to EBNA-LP phosphorylated p53 or EBNA-LP in vitro, and the phosphorylation of EBNA-LP was inhibited by Wortmannin, a specific in vitro inhibitor of DNA-PKcs.
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Affiliation(s)
- I Han
- Channing Laboratory, Harvard Medical School, Boston, Massachusetts 02445, USA
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21
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Martins SB, Eide T, Steen RL, Jahnsen T, Skålhegg B S, Collas P. HA95 is a protein of the chromatin and nuclear matrix regulating nuclear envelope dynamics. J Cell Sci 2000; 113 Pt 21:3703-13. [PMID: 11034899 DOI: 10.1242/jcs.113.21.3703] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We report a role for HA95, a nuclear protein with high homology to the nuclear A-kinase anchoring protein AKAP95, in the regulation of nuclear envelope-chromatin interactions. Biochemical and photobleaching data indicate that HA95 is tightly associated with chromatin and the nuclear matrix/lamina network in interphase, and bound to chromatin at mitosis. HA95 resides in a complex together with lamin B receptor (LBR), lamina-associated polypeptide (LAP)2 and emerin, integral proteins of the inner nuclear membrane. Cross-linking experiments, however, illustrate a tight association of HA95 with LBR and LAP2 only. Intra-nuclear blocking of HA95 with anti-HA95 antibodies abolishes nuclear breakdown in a mitotic HeLa cell extract. The antibodies inhibit nuclear membrane breakdown and chromatin condensation - the latter independently of nuclear membranes. However, lamina disassembly is not affected, as judged by immunological analyses of A/C- and B-type lamins. In contrast, immunoblocking of HA95 bound to condensed chromosomes does not impair chromatin decondensation, nuclear membrane reassembly or lamina reformation. Our results argue for a role for HA95 in anchoring nuclear membranes and lamins to chromatin in interphase, and in releasing membranes from chromatin at mitosis. The data also suggest that HA95 is not involved in initial binding of membranes to chromatin upon nuclear reassembly. We propose that HA95 is a central platform at the chromatin/nuclear matrix interface implicated in regulating nuclear envelope-chromatin interactions during the cell cycle.
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Affiliation(s)
- S B Martins
- Institute of Medical Biochemistry, University of Oslo, PO Box 1112 Blindern, Norway
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22
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Westberg C, Yang JP, Tang H, Reddy TR, Wong-Staal F. A novel shuttle protein binds to RNA helicase A and activates the retroviral constitutive transport element. J Biol Chem 2000; 275:21396-401. [PMID: 10748171 DOI: 10.1074/jbc.m909887199] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The constitutive transport element (CTE) of type D retroviruses mediates the nuclear export of unspliced viral transcripts. We previously showed that RNA helicase A functionally interacts with CTE and contains a bidirectional nuclear transport domain at the carboxyl terminus. Here we report the identification of a novel human protein, helicase A-binding protein 95 (HAP95), which specifically binds to the carboxyl terminus of RNA helicase A. HAP95 is partially homologous to AKAP95, a member of the A kinase-anchoring protein family, but lacks the protein kinase A binding domain characteristic of this family. HAP95 is a nuclear protein at steady state but shuttles between the nucleus and cytoplasm. Overexpression of HAP95 significantly increases CTE-dependent gene expression but has no effect on general gene expression or that mediated by the Rev/Rev response element of human immunodeficiency virus type 1.
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Affiliation(s)
- C Westberg
- Departments of Biology and Medicine, University of California, San Diego, La Jolla, California 92093-0665, USA
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