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Smith E, Meyerrose TE, Kohler T, Namdar-Attar M, Bab N, Lahat O, Noh T, Li J, Karaman MW, Hacia JG, Chen TT, Nolta JA, Müller R, Bab I, Frenkel B. Leaky ribosomal scanning in mammalian genomes: significance of histone H4 alternative translation in vivo. Nucleic Acids Res 2005; 33:1298-308. [PMID: 15741183 PMCID: PMC552952 DOI: 10.1093/nar/gki248] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Like alternative splicing, leaky ribosomal scanning (LRS), which occurs at suboptimal translational initiation codons, increases the physiological flexibility of the genome by allowing alternative translation. Comprehensive analysis of 22 208 human mRNAs indicates that, although the most important positions relative to the first nucleotide of the initiation codon, −3 and +4, are usually such that support initiation (A−3 = 42%, G−3 = 36% and G+4 = 47%), only 37.4% of the genes adhere to the purine (R)−3/G+4 rule at both positions simultaneously, suggesting that LRS may occur in some of the remaining (62.6%) genes. Moreover, 12.5% of the genes lack both R−3 and G+4, potentially leading to sLRS. Compared with 11 genes known to undergo LRS, 10 genes with experimental evidence for high fidelity A+1T+2G+3 initiation codons adhered much more strongly to the R−3/G+4 rule. Among the intron-less histone genes, only the H3 genes adhere to the R−3/G+4 rule, while the H1, H2A, H2B and H4 genes usually lack either R−3 or G+4. To address in vivo the significance of the previously described LRS of H4 mRNAs, which results in alternative translation of the osteogenic growth peptide, transgenic mice were engineered that ubiquitously and constitutively express a mutant H4 mRNA with an A+1→T+1 mutation. These transgenic mice, in particular the females, have a high bone mass phenotype, attributable to increased bone formation. These data suggest that many genes may fulfill cryptic functions by LRS.
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Affiliation(s)
- Elisheva Smith
- Department of Orthopaedic Surgery, University of Southern CaliforniaLos Angeles, CA 90033, USA
- Institute for Genetic Medicine, University of Southern CaliforniaLos Angeles, CA 90033, USA
| | - Todd E. Meyerrose
- Department of Pediatrics, University of Southern CaliforniaLos Angeles, CA 90033, USA
- Children's HospitalLos Angeles, CA 90033, USA
| | - Thomas Kohler
- Institute for Biomedical Engineering, Swiss Federal Institute of Technology (ETH) and University of Zurich8044 Zurich, Switzerland
| | - Malka Namdar-Attar
- Bone Laboratory, The Hebrew University of JerusalemJerusalem 91120, Israel
| | - Natti Bab
- Bone Laboratory, The Hebrew University of JerusalemJerusalem 91120, Israel
| | - Olga Lahat
- Bone Laboratory, The Hebrew University of JerusalemJerusalem 91120, Israel
| | - Tommy Noh
- Department of Biochemistry and Molecular Biology, University of Southern CaliforniaLos Angeles, CA 90033, USA
- Institute for Genetic Medicine, University of Southern CaliforniaLos Angeles, CA 90033, USA
| | - Jingjing Li
- Department of Molecular and Computational Biology, University of Southern CaliforniaLos Angeles, CA 90033, USA
| | - Mazen W. Karaman
- Department of Biochemistry and Molecular Biology, University of Southern CaliforniaLos Angeles, CA 90033, USA
- Institute for Genetic Medicine, University of Southern CaliforniaLos Angeles, CA 90033, USA
| | - Joseph G. Hacia
- Department of Biochemistry and Molecular Biology, University of Southern CaliforniaLos Angeles, CA 90033, USA
- Institute for Genetic Medicine, University of Southern CaliforniaLos Angeles, CA 90033, USA
| | - Ting T. Chen
- Department of Molecular and Computational Biology, University of Southern CaliforniaLos Angeles, CA 90033, USA
| | - Jan A. Nolta
- Department of Pediatrics, University of Southern CaliforniaLos Angeles, CA 90033, USA
- Children's HospitalLos Angeles, CA 90033, USA
| | - Ralph Müller
- Institute for Biomedical Engineering, Swiss Federal Institute of Technology (ETH) and University of Zurich8044 Zurich, Switzerland
| | - Itai Bab
- Bone Laboratory, The Hebrew University of JerusalemJerusalem 91120, Israel
| | - Baruch Frenkel
- Department of Orthopaedic Surgery, University of Southern CaliforniaLos Angeles, CA 90033, USA
- Department of Biochemistry and Molecular Biology, University of Southern CaliforniaLos Angeles, CA 90033, USA
- Institute for Genetic Medicine, University of Southern CaliforniaLos Angeles, CA 90033, USA
- To whom correspondence should be addressed at Institute for Genetic Medicine, University of Southern California, 2250 Alcazar Street, CSC/IGM 240 Los Angeles, CA 90033, USA. Tel: +1 323 442 1322; Fax: +1 323 442 2764;
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Frønsdal K, Saatcioglu F. Histone deacetylase inhibitors differentially mediate apoptosis in prostate cancer cells. Prostate 2005; 62:299-306. [PMID: 15389787 DOI: 10.1002/pros.20140] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND Histone deacetylase (HDAC) inhibitors have shown significant anti-proliferative and apoptotic properties on various cancer cells, including prostate cancer, and are therefore being evaluated as treatment modalities. However, the specific effect of HDAC inhibitors on androgen-sensitive and androgen-independent cell lines have not been thoroughly studied which we hypothesized could be different. We therefore assessed whether three structurally unrelated HDAC inhibitors, trichostatin A (TSA), depsipeptide (FR901228), and sodium butyrate, affect cell death in the prostate cancer cell lines LNCaP, DU-145, and PC-3. METHODS To investigate the extent and the nature of cell death, we used Trypan blue exclusion assay, phase-contrast light microscopy, fluorescence microscopy, and Western blot analyses. RESULTS At concentrations where they potentiate transcriptional activation, all three HDAC inhibitors induced cell death in LNCaP and DU-145 cells, but not in PC-3 cells, within the timeline of the experiments. HDAC inhibitor-induced cell death in LNCaP and DU-145 cells showed several characteristic apoptotic features, such as cell shrinkage, nuclear condensation, and poly(ADP) ribose polymerase cleavage. However, there were differences in the way LNCaP and DU-145 cells responded to treatment with various HDAC inhibitors. For example, whereas TSA and FR901228 were more effective in inducing apoptosis in LNCaP cells compared with DU-145 cells, the reverse was true for sodium butyrate. Moreover, within the same cell line, TSA, FR901228, and sodium butyrate exhibited different potencies for induction of apoptosis. CONCLUSIONS Collectively, these results suggest that the response of prostate cancer cells to HDAC inhibitors is not uniform, but cell line and inhibitor specific. Given that prostate cancer is generally a multiclonal disease representing different cell lineages, it is important to develop HDAC inhibitors that will be effective against all of these cell types.
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Affiliation(s)
- Katrine Frønsdal
- Department of Molecular Biosciences, University of Oslo, Oslo, Norway
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Kaiser C, James SR. Acetylation of insulin receptor substrate-1 is permissive for tyrosine phosphorylation. BMC Biol 2004; 2:23. [PMID: 15522123 PMCID: PMC529456 DOI: 10.1186/1741-7007-2-23] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2004] [Accepted: 11/02/2004] [Indexed: 12/21/2022] Open
Abstract
Background Insulin receptor substrate (IRS) proteins are key moderators of insulin action. Their specific regulation determines downstream protein-protein interactions and confers specificity on growth factor signalling. Regulatory mechanisms that have been identified include phosphorylation of IRS proteins on tyrosine and serine residues and ubiquitination of lysine residues. This study investigated other potential molecular mechanisms of IRS-1 regulation. Results Using the sos recruitment yeast two-hybrid system we found that IRS-1 and histone deacetylase 2 (HDAC2) interact in the cytoplasmic compartment of yeast cells. The interaction mapped to the C-terminus of IRS-1 and was confirmed through co-immunoprecipitation in vitro of recombinant IRS-1 and HDAC2. HDAC2 bound to IRS-1 in mammalian cells treated with phorbol ester or after prolonged treatment with insulin/IGF-1 and also in the livers of ob/ob mice but not PTP1B knockout mice. Thus, the association occurs under conditions of compromised insulin signalling. We found that IRS-1 is an acetylated protein, of which the acetylation is increased by treatment of cells with Trichostatin A (TSA), an inhibitor of HDAC activity. TSA-induced increases in acetylation of IRS-1 were concomitant with increases in tyrosine phosphorylation in response to insulin. These effects were confirmed using RNA interference against HDAC2, indicating that HDAC2 specifically prevents phosphorylation of IRS-1 by the insulin receptor. Conclusions Our results show that IRS-1 is an acetylated protein, a post-translational modification that has not been previously described. Acetylation of IRS-1 is permissive for tyrosine phosphorylation and facilitates insulin-stimulated signal transduction. Specific inhibition of HDAC2 may increase insulin sensitivity in otherwise insulin resistant conditions.
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Affiliation(s)
- Christina Kaiser
- Section of Cell Biology, Department of Biology, Biovitrum AB, SE-112 76, Stockholm, Sweden
| | - Stephen R James
- Section of Cell Biology, Department of Biology, Biovitrum AB, SE-112 76, Stockholm, Sweden
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Abstract
Histone deacetylases (HDACs) are enzymes that catalyze the removal of acetyl groups from lysine residues in both histone and non-histone proteins. They play a key role in the regulation of gene transcription and many other biological processes involving chromatin. Significantly, recent studies suggest that HDACs are critically involved in cell-cycle regulation, cell proliferation, differentiation, and in the development of human cancer. HDAC inhibitors currently are being exploited as potential anti-cancer agents. As expected for vital regulators of many cellular processes, the activities of HDACs are tightly controlled and precisely regulated by multiple mechanisms. The activities of most if not all HDACs are regulated by protein-protein interactions. In addition, many HDACs are regulated by post-translational modifications as well as by subcellular localization. Less studied, but perhaps equally important, is the regulation of some HDACs by control of expression, availability of cofactors, and by proteolytic processing. A complete understanding of how HDACs are regulated will contribute not only to our overall knowledge of chromatin structure and gene control, but will offer tremendous insight into approaches for developing therapeutic HDAC inhibitors with improved specificity.
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Affiliation(s)
- Nilanjan Sengupta
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, USA
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