1
|
Cohn GM, Liefwalker DF, Langer EM, Sears RC. PIN1 Provides Dynamic Control of MYC in Response to Extrinsic Signals. Front Cell Dev Biol 2020; 8:224. [PMID: 32300594 PMCID: PMC7142217 DOI: 10.3389/fcell.2020.00224] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 03/16/2020] [Indexed: 01/05/2023] Open
Abstract
PIN1 is a phosphorylation-directed member of the peptidyl-prolyl cis/trans isomerase (PPIase) family that facilitates conformational changes in phosphorylated targets such as c-MYC (MYC). Following signaling events that mediate phosphorylation of MYC at Serine 62, PIN1 establishes structurally distinct pools of MYC through its trans-cis and cis-trans isomerization activity at Proline 63. Through these isomerization steps, PIN1 functionally regulates MYC's stability, the molecular timing of its DNA binding and transcriptional activity, and its subnuclear localization. Recently, our group showed that Serine 62 phosphorylated MYC can associate with the inner basket of the nuclear pore (NP) in a PIN1-dependent manner. The poised euchromatin at the NP basket enables rapid cellular response to environmental signals and cell stress, and PIN1-mediated trafficking of MYC calibrates this response. In this perspective, we describe the molecular aspects of PIN1 target recognition and PIN1's function in the context of its temporal and spatial regulation of MYC.
Collapse
Affiliation(s)
- Gabriel M Cohn
- Department of Molecular and Medical Genetics, School of Medicine, Oregon Health and Science University, Portland, OR, United States
| | - Daniel F Liefwalker
- Department of Molecular and Medical Genetics, School of Medicine, Oregon Health and Science University, Portland, OR, United States
| | - Ellen M Langer
- Department of Molecular and Medical Genetics, School of Medicine, Oregon Health and Science University, Portland, OR, United States.,Knight Cancer Institute, Oregon Health and Science University, Portland, OR, United States
| | - Rosalie C Sears
- Department of Molecular and Medical Genetics, School of Medicine, Oregon Health and Science University, Portland, OR, United States.,Knight Cancer Institute, Oregon Health and Science University, Portland, OR, United States.,Brenden-Colson Center for Pancreatic Care, Oregon Health and Science University, Portland, OR, United States
| |
Collapse
|
2
|
Su Y, Pelz C, Huang T, Torkenczy K, Wang X, Cherry A, Daniel CJ, Liang J, Nan X, Dai MS, Adey A, Impey S, Sears RC. Post-translational modification localizes MYC to the nuclear pore basket to regulate a subset of target genes involved in cellular responses to environmental signals. Genes Dev 2018; 32:1398-1419. [PMID: 30366908 PMCID: PMC6217735 DOI: 10.1101/gad.314377.118] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 09/04/2018] [Indexed: 12/14/2022]
Abstract
In this study, Su et al. investigate how post-translational modifications of Myc that affect stability and oncogenic activity regulate its function. They show that Ser62 phosphorylation and PIN1-mediated isomerization of MYC dynamically regulate the spatial distribution of MYC in the nucleus, promoting its association with the inner basket of the nuclear pore in response to proliferative signals, where it recruits the histone acetyltransferase GCN5 to bind and regulate local gene acetylation and expression, thus providing new insights into how post-translational modification of MYC controls its spatial activity. The transcription factor MYC (also c-Myc) induces histone modification, chromatin remodeling, and the release of paused RNA polymerase to broadly regulate transcription. MYC is subject to a series of post-translational modifications that affect its stability and oncogenic activity, but how these control MYC's function on the genome is largely unknown. Recent work demonstrates an intimate connection between nuclear compartmentalization and gene regulation. Here, we report that Ser62 phosphorylation and PIN1-mediated isomerization of MYC dynamically regulate the spatial distribution of MYC in the nucleus, promoting its association with the inner basket of the nuclear pore in response to proliferative signals, where it recruits the histone acetyltransferase GCN5 to bind and regulate local gene acetylation and expression. We demonstrate that PIN1-mediated localization of MYC to the nuclear pore regulates MYC target genes responsive to mitogen stimulation that are involved in proliferation and migration pathways. These changes are also present at the chromatin level, with an increase in open regulatory elements in response to stimulation that is PIN1-dependent and associated with MYC chromatin binding. Taken together, our study indicates that post-translational modification of MYC controls its spatial activity to optimally regulate gene expression in response to extrinsic signals in normal and diseased states.
Collapse
Affiliation(s)
- Yulong Su
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Oregon 97239, USA
| | - Carl Pelz
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Oregon 97239, USA.,Oregon Stem Cell Center, Oregon Health and Science University, Oregon 97239, USA
| | - Tao Huang
- Department of Biomedical Engineering, Oregon Health and Science University, Oregon 97239, USA
| | - Kristof Torkenczy
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Oregon 97239, USA
| | - Xiaoyan Wang
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Oregon 97239, USA
| | - Allison Cherry
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Oregon 97239, USA
| | - Colin J Daniel
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Oregon 97239, USA
| | - Juan Liang
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Oregon 97239, USA
| | - Xiaolin Nan
- Department of Biomedical Engineering, Oregon Health and Science University, Oregon 97239, USA
| | - Mu-Shui Dai
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Oregon 97239, USA
| | - Andrew Adey
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Oregon 97239, USA
| | - Soren Impey
- Oregon Stem Cell Center, Oregon Health and Science University, Oregon 97239, USA
| | - Rosalie C Sears
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Oregon 97239, USA
| |
Collapse
|
3
|
Abstract
Prefoldin is a cochaperone, present in all eukaryotes, that cooperates with the chaperonin CCT. It is known mainly for its functional relevance in the cytoplasmic folding of actin and tubulin monomers during cytoskeleton assembly. However, both canonical and prefoldin-like subunits of this heterohexameric complex have also been found in the nucleus, and are functionally connected with nuclear processes in yeast and metazoa. Plant prefoldin has also been detected in the nucleus and physically associated with a gene regulator. In this review, we summarize the information available on the involvement of prefoldin in nuclear phenomena, place special emphasis on gene transcription, and discuss the possibility of a global coordination between gene regulation and cytoplasmic dynamics mediated by prefoldin.
Collapse
Affiliation(s)
- Gonzalo Millán-Zambrano
- Instituto de Biomedicina de Sevilla, Hospital Virgen del Rocío-CSIC-Universidad de Sevilla, 41013 Seville, Spain Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - Sebastián Chávez
- Instituto de Biomedicina de Sevilla, Hospital Virgen del Rocío-CSIC-Universidad de Sevilla, 41013 Seville, Spain Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| |
Collapse
|
4
|
Bouayad D, Pederzoli-Ribeil M, Mocek J, Candalh C, Arlet JB, Hermine O, Reuter N, Davezac N, Witko-Sarsat V. Nuclear-to-cytoplasmic relocalization of the proliferating cell nuclear antigen (PCNA) during differentiation involves a chromosome region maintenance 1 (CRM1)-dependent export and is a prerequisite for PCNA antiapoptotic activity in mature neutrophils. J Biol Chem 2012; 287:33812-25. [PMID: 22846997 PMCID: PMC3460476 DOI: 10.1074/jbc.m112.367839] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 07/24/2012] [Indexed: 01/03/2023] Open
Abstract
Neutrophils are deprived of proliferative capacity and have a tightly controlled lifespan to avoid their persistence at the site of injury. We have recently described that the proliferating cell nuclear antigen (PCNA), a nuclear factor involved in DNA replication and repair of proliferating cells, is a key regulator of neutrophil survival. In neutrophils, PCNA was localized exclusively in the cytoplasm due to its nuclear-to-cytoplasmic relocalization during granulocytic differentiation. We showed here that leptomycin B, an inhibitor of the chromosome region maintenance 1 (CRM1) exportin, inhibited PCNA relocalization during granulocytic differentiation of HL-60 and NB4 promyelocytic cell lines and of human CD34(+) primary cells. Using enhanced green fluorescent protein fusion constructs, we have demonstrated that PCNA relocalization involved a nuclear export signal (NES) located from Ile-11 to Ile-23 in the PCNA sequence. However, this NES, located at the inner face of the PCNA trimer, was not functional in wild-type PCNA, but instead, was fully active and leptomycin B-sensitive in the monomeric PCNAY114A mutant. To test whether a defect in PCNA cytoplasmic relocalization would affect its antiapoptotic activity in mature neutrophils, a chimeric PCNA fused with the SV40 nuclear localization sequence (NLS) was generated to preclude its cytoplasmic localization. As expected, neutrophil-differentiated PLB985 cells expressing ectopic SV40NLS-PCNA had an increased nuclear PCNA as compared with cells expressing wild-type PCNA. Accordingly, the nuclear PCNA mutant did not show any antiapoptotic activity as compared with wild-type PCNA. Nuclear-to-cytoplasmic relocalization that occurred during myeloid differentiation is essential for PCNA antiapoptotic activity in mature neutrophils and is dependent on the newly identified monomerization-dependent PCNA NES.
Collapse
Affiliation(s)
- Dikra Bouayad
- From the INSERM U1016, 75014 Paris, France
- the Institut Cochin, Université Paris Descartes, Cochin Hospital, 75015 Paris, France
- the CNRS UMR8104, 75014 Paris, France
| | - Magali Pederzoli-Ribeil
- From the INSERM U1016, 75014 Paris, France
- the Institut Cochin, Université Paris Descartes, Cochin Hospital, 75015 Paris, France
- the CNRS UMR8104, 75014 Paris, France
| | - Julie Mocek
- From the INSERM U1016, 75014 Paris, France
- the Institut Cochin, Université Paris Descartes, Cochin Hospital, 75015 Paris, France
- the CNRS UMR8104, 75014 Paris, France
| | - Céline Candalh
- From the INSERM U1016, 75014 Paris, France
- the Institut Cochin, Université Paris Descartes, Cochin Hospital, 75015 Paris, France
- the CNRS UMR8104, 75014 Paris, France
| | | | - Olivier Hermine
- the CNRS UMR8147 and
- Hematology Department, Université Paris Descartes, Necker Hospital, 75015 Paris, France
| | - Nathalie Reuter
- the Computational Biology Unit, University of Bergen, N-5008 Bergen, Norway, and
| | - Noélie Davezac
- CNRS UMR5547, Université Toulouse III, 31400 Toulouse, France
| | - Véronique Witko-Sarsat
- From the INSERM U1016, 75014 Paris, France
- the Institut Cochin, Université Paris Descartes, Cochin Hospital, 75015 Paris, France
- the CNRS UMR8104, 75014 Paris, France
| |
Collapse
|
5
|
Estrada-Bernal A, Sanford SD, Sosa LJ, Simon GC, Hansen KC, Pfenninger KH. Functional complexity of the axonal growth cone: a proteomic analysis. PLoS One 2012; 7:e31858. [PMID: 22384089 PMCID: PMC3288056 DOI: 10.1371/journal.pone.0031858] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Accepted: 01/17/2012] [Indexed: 11/19/2022] Open
Abstract
The growth cone, the tip of the emerging neurite, plays a crucial role in establishing the wiring of the developing nervous system. We performed an extensive proteomic analysis of axonal growth cones isolated from the brains of fetal Sprague-Dawley rats. Approximately 2000 proteins were identified at ≥ 99% confidence level. Using informatics, including functional annotation cluster and KEGG pathway analysis, we found great diversity of proteins involved in axonal pathfinding, cytoskeletal remodeling, vesicular traffic and carbohydrate metabolism, as expected. We also found a large and complex array of proteins involved in translation, protein folding, posttranslational processing, and proteasome/ubiquitination-dependent degradation. Immunofluorescence studies performed on hippocampal neurons in culture confirmed the presence in the axonal growth cone of proteins representative of these processes. These analyses also provide evidence for rough endoplasmic reticulum and reveal a reticular structure equipped with Golgi-like functions in the axonal growth cone. Furthermore, Western blot revealed the growth cone enrichment, relative to fetal brain homogenate, of some of the proteins involved in protein synthesis, folding and catabolism. Our study provides a resource for further research and amplifies the relatively recently developed concept that the axonal growth cone is equipped with proteins capable of performing a highly diverse range of functions.
Collapse
Affiliation(s)
- Adriana Estrada-Bernal
- Department of Pediatrics and Colorado Intellectual and Developmental Disabilities Research Center, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Staci D. Sanford
- Department of Pediatrics and Colorado Intellectual and Developmental Disabilities Research Center, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Lucas J. Sosa
- Department of Pediatrics and Colorado Intellectual and Developmental Disabilities Research Center, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Glenn C. Simon
- Department of Pediatrics and Colorado Intellectual and Developmental Disabilities Research Center, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Kirk C. Hansen
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Karl H. Pfenninger
- Department of Pediatrics and Colorado Intellectual and Developmental Disabilities Research Center, University of Colorado School of Medicine, Aurora, Colorado, United States of America
- * E-mail:
| |
Collapse
|
6
|
Abstract
c-Myc (Myc) is a well known transcription factor that regulates many essential cellular processes; however, its role in modulating immunity is not known. Here, we showed different species of mycobacteria can induce Myc expression via ERK1/2 and JNK activation. Unexpectedly, the induced Myc is localized in the cytoplasm but not in the nucleus. This induced Myc expression is associated with the induction of TNF-α and IL-6 and with the suppression of intracellular mycobacterial growth. To delineate the underlying mechanisms, we demonstrated that Myc enhances IRAK1 degradation, leading to specific activations of ERK1/2 and p38 MAPK but not Akt, and reduces IκBα protein recovery upon degradation. Hence, our findings may provide insights into a potential role for Myc in regulating the antimicrobial responses.
Collapse
|
7
|
Mistafa O, Ghalali A, Kadekar S, Högberg J, Stenius U. Purinergic receptor-mediated rapid depletion of nuclear phosphorylated Akt depends on pleckstrin homology domain leucine-rich repeat phosphatase, calcineurin, protein phosphatase 2A, and PTEN phosphatases. J Biol Chem 2010; 285:27900-10. [PMID: 20605778 DOI: 10.1074/jbc.m110.117093] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Akt is an important oncoprotein, and data suggest a critical role for nuclear Akt in cancer development. We have previously described a rapid (3-5 min) and P2X7-dependent depletion of nuclear phosphorylated Akt (pAkt) and effects on downstream targets, and here we studied mechanisms behind the pAkt depletion. We show that cholesterol-lowering drugs, statins, or extracellular ATP, induced a complex and coordinated response in insulin-stimulated A549 cells leading to depletion of nuclear pAkt. It involved protein/lipid phosphatases PTEN, pleckstrin homology domain leucine-rich repeat phosphatase (PHLPP1 and -2), protein phosphatase 2A (PP2A), and calcineurin. We employed immunocytology, immunoprecipitation, and proximity ligation assay techniques and show that PHLPP and calcineurin translocated to the nucleus and formed complexes with Akt within 3 min. Also PTEN translocated to the nucleus and then co-localized with pAkt close to the nuclear membrane. An inhibitor of the scaffolding immunophilin FK506-binding protein 51 (FKBP51) and calcineurin, FK506, prevented depletion of nuclear pAkt. Furthermore, okadaic acid, an inhibitor of PP2A, prevented the nuclear pAkt depletion. Chemical inhibition and siRNA indicated that PHLPP, PP2A, and PTEN were required for a robust depletion of nuclear pAkt, and in prostate cancer cells lacking PTEN, transfection of PTEN restored the statin-induced pAkt depletion. The activation of protein and lipid phosphatases was paralleled by a rapid proliferating cell nuclear antigen (PCNA) translocation to the nucleus, a PCNA-p21(cip1) complex formation, and cyclin D1 degradation. We conclude that these effects reflect a signaling pathway for rapid depletion of pAkt that may stop the cell cycle.
Collapse
Affiliation(s)
- Oras Mistafa
- Institute of Environmental Medicine, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | | | | | | | | |
Collapse
|
8
|
Malnou CE, Brockly F, Favard C, Moquet-Torcy G, Piechaczyk M, Jariel-Encontre I. Heterodimerization with different Jun proteins controls c-Fos intranuclear dynamics and distribution. J Biol Chem 2010; 285:6552-62. [PMID: 20053986 DOI: 10.1074/jbc.m109.032680] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The c-Fos proto-oncogenic transcription factor defines a multigene family controlling many processes both at the cell and the whole organism level. To bind to its target AP-1/12-O-tetradecanoylphorbol-13-acetate-responsive element or cAMP-responsive element DNA sequences in gene promoters and exert its transcriptional part, c-Fos must heterodimerize with other bZip proteins, its best studied partners being the Jun proteins (c-Jun, JunB, and JunD). c-Fos expression is regulated at many transcriptional and post-transcriptional levels, yet little is known on how its localization is dynamically regulated in the cell. Here we have investigated its intranuclear mobility using fluorescence recovery after photobleaching, genetic, and biochemical approaches. Whereas monomeric c-Fos is highly mobile and distributed evenly with nucleolar exclusion in the nucleus, heterodimerization with c-Jun entails intranuclear redistribution and dramatic reduction in mobility of c-Fos caused by predominant association with the nuclear matrix independently of any binding to AP-1/12-O-tetradecanoylphorbol-13-acetate-responsive element or cAMP-responsive element sequences. In contrast to c-Jun, dimerization with JunB does not detectably affect c-Fos mobility. However, dimerization with JunB affects intranuclear distribution with significant differences in the localization of c-Fos.c-Jun and c-Fos.JunB dimers. Moreover, c-Jun and JunB exert comparable effects on another Fos family member, Fra-1. Thus, we report a novel regulation, i.e. differentially regulated intranuclear mobility and distribution of Fos proteins by their Jun partners, and suggest the existence of intranuclear storage sites for latent c-Fos.c-Jun AP-1 complexes. This may affect the numerous physiopathological functions these transcription factors control.
Collapse
Affiliation(s)
- Cécile E Malnou
- Institut de Génétique Moléculaire de Montpellier, UMR5535, CNRS, 1919 route de Mende, 34293 Montpellier Cedex 5, France
| | | | | | | | | | | |
Collapse
|
9
|
Kakar M, Davis JR, Kern SE, Lim CS. Optimizing the protein switch: altering nuclear import and export signals, and ligand binding domain. J Control Release 2007; 120:220-32. [PMID: 17574289 PMCID: PMC2041942 DOI: 10.1016/j.jconrel.2007.04.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Revised: 04/16/2007] [Accepted: 04/26/2007] [Indexed: 11/25/2022]
Abstract
Ligand regulated localization controllable protein constructs were optimized in this study. Several constructs were made from a classical nuclear export signal (HIV-rev, MAPKK, or progesterone receptor) in combination with a SV40 T-antigen type nuclear import signal. Different ligand binding domains (LBDs from glucocorticoid receptor or progesterone receptor) were also tested for their ability to impart control over localization of proteins. This study was designed to create constructs which are cytoplasmic in the absence of ligand and nuclear in the presence of ligand, and also to regulate the amount of protein translocating to the nucleus on ligand induction. The balance between the strengths of import and export signals was critical for overall localization of proteins. The amount of protein entering the nucleus was also affected by the dose of ligand (10-100 nM). However, the overall import characteristics were determined by the strengths of localization signals and the inherent localization properties of the LBD used. This study established that the amount of protein present in a particular compartment can be regulated by the use of localization signals of various strengths. These optimized localization controllable protein constructs can be used to correct for diseases due to aberrant localization of proteins.
Collapse
MESH Headings
- Active Transport, Cell Nucleus
- Adenocarcinoma/pathology
- Amino Acid Sequence
- Animals
- Antigens, Polyomavirus Transforming/genetics
- Antigens, Polyomavirus Transforming/metabolism
- Cell Line, Tumor
- Cell Nucleus/metabolism
- Cytoplasm/metabolism
- Dexamethasone
- Electroporation
- Gene Products, rev/genetics
- Gene Products, rev/metabolism
- Ligands
- Mice
- Mifepristone
- Mitogen-Activated Protein Kinase Kinases/genetics
- Mitogen-Activated Protein Kinase Kinases/metabolism
- Nuclear Export Signals/physiology
- Plasmids
- Protein Structure, Tertiary
- Protein Transport
- Proteins/genetics
- Proteins/metabolism
- Receptors, Glucocorticoid/genetics
- Receptors, Glucocorticoid/metabolism
- Receptors, Progesterone/genetics
- Receptors, Progesterone/metabolism
Collapse
Affiliation(s)
- Mudit Kakar
- Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, 421 Wakara Way # 318, Salt Lake City, UT 84108, USA
| | - James R. Davis
- Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, 421 Wakara Way # 318, Salt Lake City, UT 84108, USA
| | - Steve E. Kern
- Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, 421 Wakara Way # 318, Salt Lake City, UT 84108, USA
- Department of Anesthesiology, University of Utah, Salt Lake City UT 84132, USA
| | - Carol S. Lim
- Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, 421 Wakara Way # 318, Salt Lake City, UT 84108, USA
- Corresponding author. Tel: 801-587-9711 Fax: 801-585-3614, E-mail address:
| |
Collapse
|
10
|
Nair M, Teng A, Bilanchone V, Agrawal A, Li B, Dai X. Ovol1 regulates the growth arrest of embryonic epidermal progenitor cells and represses c-myc transcription. ACTA ACUST UNITED AC 2006; 173:253-64. [PMID: 16636146 PMCID: PMC2063816 DOI: 10.1083/jcb.200508196] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Transcriptional control plays a key role in regulating epidermal proliferation and differentiation. Although ample information has been obtained on how epidermal homeostasis is controlled in adult skin, less is known about the control of proliferation/differentiation of epidermal stem/progenitor cells in the developing embryo. Ovol1, encoding a zinc finger protein homologous to Drosophila melanogaster Ovo, is expressed in embryonic epidermal progenitor cells that are transiting from proliferation to terminal differentiation. In this study, we demonstrate a function for Ovol1 in interfollicular epidermal development. In its absence, developing epidermis fails to properly restrict the proliferative potential of progenitor cells, and cultured keratinocytes fail to efficiently undergo growth arrest in response to extrinsic growth-inhibitory signals. We present molecular evidence that c-myc expression is up-regulated in Ovol1-deficient suprabasal cells and that Ovol1 represses c-myc transcription by directly binding to its promoter. Collectively, our findings indicate that Ovol1 is required for proliferation exit of committed epidermal progenitor cells and identify c-myc as an Ovol1 target.
Collapse
Affiliation(s)
- Mahalakshmi Nair
- Department of Biological Chemistry, University of California, Irvine, 92697, USA
| | | | | | | | | | | |
Collapse
|
11
|
Ivorra C, Kubicek M, González JM, Sanz-González SM, Alvarez-Barrientos A, O'Connor JE, Burke B, Andrés V. A mechanism of AP-1 suppression through interaction of c-Fos with lamin A/C. Genes Dev 2006; 20:307-20. [PMID: 16452503 PMCID: PMC1361702 DOI: 10.1101/gad.349506] [Citation(s) in RCA: 171] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
AP-1 (Activating Protein 1) transcription factor activity is tightly regulated at multiple levels, including dimer formation (i.e., Fos/Jun). Here we show that the intermediate filament protein lamin A/C suppresses AP-1 function through direct interaction with c-Fos, and that both proteins can interact and colocalize at the nuclear envelope (NE) in mammalian cells. Perinuclear localization of c-Fos is absent in Lmna-null cells but can be restored by lamin A overexpression. In vitro, preincubation of c-Fos with lamin A prior to the addition of c-Jun inhibits AP-1 DNA-binding activity. In vivo, overexpression of lamin A reduces the formation of c-Fos/c-Jun heterodimers, and suppresses AP-1 DNA-binding and transcriptional activity. Notably, c-Fos colocalizes with lamin A/C at the NE in starvation-synchronized quiescent cells lacking detectable AP-1 DNA binding. In contrast, serum-induced AP-1 DNA-binding activity coincides with abundant nucleoplasmic c-Fos expression without changes in lamin A/C localization. We also found that Lmna-null cells display enhanced proliferation. In contrast, lamin A overexpression causes growth arrest, and ectopic c-Fos partially overcomes lamin A/C-induced cell cycle alterations. We propose lamin A/C-mediated c-Fos sequestration at the NE as a novel mechanism of transcriptional and cell cycle control.
Collapse
Affiliation(s)
- Carmen Ivorra
- Laboratory of Vascular Biology, Department of Molecular and Cellular Pathology and Therapy, Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Científicas, Valencia 46010, Spain
| | | | | | | | | | | | | | | |
Collapse
|
12
|
Ziegelbauer J, Wei J, Tjian R. Myc-interacting protein 1 target gene profile: a link to microtubules, extracellular signal-regulated kinase, and cell growth. Proc Natl Acad Sci U S A 2004; 101:458-63. [PMID: 14704274 PMCID: PMC327169 DOI: 10.1073/pnas.0307562100] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
To study the role of the transcription factor Myc-interacting protein 1 (MIZ-1) in activating various target genes after induction with the microtubule disrupting agent T113242, we have used small interfering RNA duplexes (siRNAs) to knockdown the expression of MIZ-1. As expected, depletion of MIZ-1 resulted in the inhibition of T113242-dependent activation of the low-density lipoprotein receptor (LDLR) gene in hepatocytes. Cells transfected with MIZ-1 siRNAs also exhibited growth arrest. In addition, inhibition of the extracellular signal-regulated kinase (ERK) pathway inhibited T113242-induced nuclear accumulation of MIZ-1 and activation of LDLR. Gene expression microarray analysis under various induction conditions identified other T113242-activated genes affected by a decrease in MIZ-1 and inhibition of the ERK pathway. We also found that the accumulation of MIZ-1 in the nucleus is influenced by cell-cell contact and/or growth. Taken together, our studies suggest that MIZ-1 regulates a specific set of genes that includes LDLR and that the ERK pathway plays a role in the activation of target promoters by MIZ-1.
Collapse
Affiliation(s)
- Joseph Ziegelbauer
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA
| | | | | |
Collapse
|
13
|
Niklinski J, Claassen G, Meyers C, Gregory MA, Allegra CJ, Kaye FJ, Hann SR, Zajac-Kaye M. Disruption of Myc-tubulin interaction by hyperphosphorylation of c-Myc during mitosis or by constitutive hyperphosphorylation of mutant c-Myc in Burkitt's lymphoma. Mol Cell Biol 2000; 20:5276-84. [PMID: 10866684 PMCID: PMC85977 DOI: 10.1128/mcb.20.14.5276-5284.2000] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Somatic mutations at Thr-58 of c-Myc have been detected in Burkitt's lymphoma (BL) tumors and have been shown to affect the transforming potential of the Myc oncoprotein. In addition, the N-terminal domain of c-Myc has been shown to interact with microtubules in vivo, and the binding of c-Myc to alpha-tubulin was localized to amino acids 48 to 135 within the c-Myc protein. We demonstrate that c-Myc proteins harboring a naturally occurring mutation at Thr-58 from BL cell lines have increased stability and are constitutively hyperphosphorylated, which disrupts the in vivo interaction of c-Myc with alpha-tubulin. In addition, we show that wild-type c-Myc-alpha-tubulin interactions are also disrupted during a transient mitosis-specific hyperphosphorylation of c-Myc, which resembles the constitutive hyperphosphorylation pattern of Thr-58 in BL cells.
Collapse
Affiliation(s)
- J Niklinski
- Department of Developmental Therapeutics, Medicine Branch, Division of Clinical Sciences, National Cancer Institute, Bethesda, Maryland 20889, USA
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Okano HJ, Park WY, Corradi JP, Darnell RB. The cytoplasmic Purkinje onconeural antigen cdr2 down-regulates c-Myc function: implications for neuronal and tumor cell survival. Genes Dev 1999; 13:2087-97. [PMID: 10465786 PMCID: PMC316965 DOI: 10.1101/gad.13.16.2087] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Paraneoplastic cerebellar degeneration (PCD) is a disorder in which breast or ovarian tumors express an onconeural antigen termed cdr2, which normally is expressed in cerebellar Purkinje neurons. This leads to an immune response to cdr2 that is associated with tumor immunity and autoimmune cerebellar degeneration. We have found that cdr2, a cytoplasmic protein harboring a helix-leucine zipper (HLZ) motif, interacts specifically with the HLZ motif of c-Myc. Both proteins colocalize in the cytoplasm of adult cerebellar Purkinje neurons, and coimmunoprecipitate from tumor cell lines and cerebellar extracts. cdr2 down-regulates c-Myc-dependent transcription in cotransfection assays, and redistributes Myc protein in the cytoplasm. Disease antisera from six of six PCD patients specifically blocked the interaction between cdr2 and c-Myc in vitro. These data indicate that cdr2 normally sequesters c-Myc in the neuronal cytoplasm, thereby down-regulating c-Myc activity, and suggest a mechanism whereby inhibition of cdr2 function by autoantibodies in PCD may contribute to Purkinje neuronal death.
Collapse
Affiliation(s)
- H J Okano
- Laboratory of Molecular Neuro-Oncology, The Rockefeller University, New York, New York 10021 USA
| | | | | | | |
Collapse
|
15
|
Orford RL, Robinson C, Haydon JM, Patient RK, Guille MJ. The maternal CCAAT box transcription factor which controls GATA-2 expression is novel and developmentally regulated and contains a double-stranded-RNA-binding subunit. Mol Cell Biol 1998; 18:5557-66. [PMID: 9710639 PMCID: PMC109140 DOI: 10.1128/mcb.18.9.5557] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/1998] [Accepted: 06/10/1998] [Indexed: 11/20/2022] Open
Abstract
The transcription factor GATA-2 is expressed at high levels in the nonneural ectoderm of the Xenopus embryo at neurula stages, with lower amounts of RNA present in the ventral mesoderm and endoderm. The promoter of the GATA-2 gene contains an inverted CCAAT box conserved among Xenopus laevis, humans, chickens, and mice. We have shown that this sequence is essential for GATA-2 transcription during early development and that the factor binding it is maternal. The DNA-binding activity of this factor is detectable in nuclei and chromatin bound only when zygotic GATA-2 transcription starts. Here we report the characterization of this factor, which we call CBTF (CCAAT box transcription factor). CBTF activity mainly appears late in oogenesis, when it is nuclear, and the complex has multiple subunits. We have identified one subunit of the factor as p122, a Xenopus double-stranded-RNA-binding protein. The p122 protein is perinuclear during early embryonic development but moves from the cytoplasm into the nuclei of embryonic cells at stage 9, prior to the detection of CBTF activity in the nucleus. Thus, the accumulation of CBTF activity in the nucleus is a multistep process. We show that the p122 protein is expressed mainly in the ectoderm. Expression of p122 mRNA is more restricted, mainly to the anterior ectoderm and mesoderm and to the neural tube. Two properties of CBTF, its dual role and its cytoplasm-to-nucleus translocation, are shared with other vertebrate maternal transcription factors and may be general properties of these proteins.
Collapse
Affiliation(s)
- R L Orford
- Biophysics Laboratories, Division of Molecular and Cell Biology, Institute of Biomolecular and Biomedical Sciences, University of Portsmouth, Portsmouth PO1 2DY, United Kingdom
| | | | | | | | | |
Collapse
|
16
|
Skouteris GG, Schröder CH. C-myc is required for the G0/G1-S transition of primary hepatocytes stimulated with a deleted form of hepatocyte growth factor. Biochem J 1996; 316 ( Pt 3):879-86. [PMID: 8670166 PMCID: PMC1217432 DOI: 10.1042/bj3160879] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Primary rat hepatocytes stimulated in vitro with the addition of a deleted form of hepatocyte growth factor (dHGF) enter the S-phase 48 h after addition of the growth factor. The c-myc gene is believed to play a role in a variety of cellular stages, such as proliferation, differentiation and cell death. In primary hepatocytes c-myc was expressed constitutively at both mRNA and protein levels, independently of the growth conditions. dHGF induced significant c-myc expression at times correlated with the long-lasting pre-S phase, and no induction was observed at the G0/G1 traverse compared with the unstimulated hepatocytes. An antisense construct coding for all three exons of c-myc was imported into hepatocytes by using the transferrin receptor-mediated endocytosis methodology (transferrinfection). Expression of the antisense construct inhibited the biosynthesis of the c-Myc protein, however it did not interfere with the expression of c-met, encoding the receptor for HGF/dHGF. Continuous expression of the antisense construct inhibited entry of the hepatocytes into the S-phase. Regulated induction of the antisense c-myc by dexamethasone for up to 6 h in culture, did not interfere with the entry of hepatocytes into the S-phase. c-myc expression was shown to be required between 6 and 12 h in dHGF-stimulated hepatocytes, and inhibition of its expression during this time by the antisense myc construct did not allow these cells to enter the S-phase. Inhibition of c-myc biosynthesis between 24 and 48 h hours slightly affected the DNA synthetic response. It is proposed that the expression of c-Myc protein interferes with the "priming' of hepatocytes to become responsive to growth-factor stimuli, or in the absence of such stimuli it interferes with the maintenance of a non-proliferating phenotype and subsequent in vitro de-differentiation.
Collapse
Affiliation(s)
- G G Skouteris
- Department of Applied Tumour Virology, Deutsches Krebsforschungszentrum, Heidelberg, Germany
| | | |
Collapse
|
17
|
Alexandrova N, Niklinski J, Bliskovsky V, Otterson GA, Blake M, Kaye FJ, Zajac-Kaye M. The N-terminal domain of c-Myc associates with alpha-tubulin and microtubules in vivo and in vitro. Mol Cell Biol 1995; 15:5188-95. [PMID: 7651436 PMCID: PMC230766 DOI: 10.1128/mcb.15.9.5188] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The polymerization of alpha- and beta-tubulin into microtubules results in a complex network of microfibrils that have important structural and functional roles in all eukaryotic cells. In addition, microtubules can interact with a diverse family of polypeptides which are believed to directly promote the assembly of microtubules and to modulate their functional activity. We have demonstrated that the c-Myc oncoprotein interacts in vivo and in vitro with alpha-tubulin and with polymerized microtubules and have defined the binding site to the N-terminal region within the transactivation domain of c-Myc. In addition, we have shown that c-Myc colocalizes with microtubules and remains tightly bound to the microtubule network after detergent extraction of intact cells. These findings suggest a potential role for Myc-tubulin interaction in vivo.
Collapse
Affiliation(s)
- N Alexandrova
- Laboratory of Biological Chemistry, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | | | | | | | | | |
Collapse
|
18
|
Gauthier-Rouvière C, Vandromme M, Lautredou N, Cai QQ, Girard F, Fernandez A, Lamb N. The serum response factor nuclear localization signal: general implications for cyclic AMP-dependent protein kinase activity in control of nuclear translocation. Mol Cell Biol 1995; 15:433-44. [PMID: 7799952 PMCID: PMC231986 DOI: 10.1128/mcb.15.1.433] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We have identified a basic sequence in the N-terminal region of the 67-kDa serum response factor (p67SRF or SRF) responsible for its nuclear localization. A peptide containing this nuclear localization signal (NLS) translocates rabbit immunoglobulin G (IgG) into the nucleus as efficiently as a peptide encoding the simian virus 40 NLS. This effect is abolished by substituting any two of the four basic residues in this NLS. Overexpression of a modified form of SRF in which these basic residues have been mutated confirms the absolute requirement for this sequence, and not the other basic amino acid sequences adjacent to it, in the nuclear localization of SRF. Since this NLS is in close proximity to potential phosphorylation sites for the cAMP-dependent protein kinase (A-kinase), we further investigated if A-kinase plays a role in the nuclear location of SRF. The nuclear transport of SRF proteins requires basal A-kinase activity, since inhibition of A-kinase by using either the specific inhibitory peptide PKIm or type II regulatory subunits (RII) completely prevents the nuclear localization of plasmid-expressed tagged SRF or an SRF-NLS-IgG conjugate. Direct phosphorylation of SRF by A-kinase can be discounted in this effect, since mutation of the putative phosphorylation sites in either the NLS peptide or the encoded full-length SRF protein had no effect on nuclear transport of the mutants. Finally, in support of an implication of A-kinase-dependent phosphorylation in a more general mechanism affecting nuclear import, we show that the nuclear transport of a simian virus 40-NLS-conjugated IgG or purified cyclin A protein is also blocked by inhibition of A-kinase, even though neither contains any potential sites for phosphorylation by A-kinase or can be phosphorylated by A-kinase in vitro.
Collapse
Affiliation(s)
- C Gauthier-Rouvière
- Cell Biology Unit, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Montpellier, France
| | | | | | | | | | | | | |
Collapse
|
19
|
Abstract
We report the fortuitous isolation of cDNA clones encoding a novel zinc finger DNA-binding protein termed BZP. The protein encoded is 114 kDa and contains eight zinc finger motifs, seven of which are present in two clusters at opposite ends of the molecule. Both finger clusters bound to the 9-bp sequence AAAGGTGCA with apparent Kds of approximately 2.5 nM. Two of the finger motifs within the amino- and carboxy-terminal finger clusters share 63% amino acid identity. BZP inhibited transcription of the herpes simplex virus thymidine kinase promoter when copies of the 9-bp target motif were linked in cis, suggesting that it functions as a transcriptional repressor. BZP mRNA and immunoreactivity were detected in several established cell lines but were most abundant in hamster insulinoma (HIT) cells, the parental source of the cDNAs. In mouse tissues, BZP mRNA and immunoreactivity were identified in cells of the endocrine pancreas, anterior pituitary, and central nervous system. Interestingly, in HIT cells proliferating in culture, BZP immunoreactivity was predominately nuclear in location, whereas it was usually located in the cytoplasm in most neural and neuroendocrine tissues. Serum deprivation of HIT cells caused BZP immunoreactivity to become predominantly cytoplasmic in location and attenuated its inhibitory effect on transcription, thereby suggesting that the both the subcellular location and the function of this protein are modulated by factors in serum.
Collapse
|
20
|
Franklin AJ, Jetton TL, Shelton KD, Magnuson MA. BZP, a novel serum-responsive zinc finger protein that inhibits gene transcription. Mol Cell Biol 1994; 14:6773-88. [PMID: 7935395 PMCID: PMC359208 DOI: 10.1128/mcb.14.10.6773-6788.1994] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We report the fortuitous isolation of cDNA clones encoding a novel zinc finger DNA-binding protein termed BZP. The protein encoded is 114 kDa and contains eight zinc finger motifs, seven of which are present in two clusters at opposite ends of the molecule. Both finger clusters bound to the 9-bp sequence AAAGGTGCA with apparent Kds of approximately 2.5 nM. Two of the finger motifs within the amino- and carboxy-terminal finger clusters share 63% amino acid identity. BZP inhibited transcription of the herpes simplex virus thymidine kinase promoter when copies of the 9-bp target motif were linked in cis, suggesting that it functions as a transcriptional repressor. BZP mRNA and immunoreactivity were detected in several established cell lines but were most abundant in hamster insulinoma (HIT) cells, the parental source of the cDNAs. In mouse tissues, BZP mRNA and immunoreactivity were identified in cells of the endocrine pancreas, anterior pituitary, and central nervous system. Interestingly, in HIT cells proliferating in culture, BZP immunoreactivity was predominately nuclear in location, whereas it was usually located in the cytoplasm in most neural and neuroendocrine tissues. Serum deprivation of HIT cells caused BZP immunoreactivity to become predominantly cytoplasmic in location and attenuated its inhibitory effect on transcription, thereby suggesting that the both the subcellular location and the function of this protein are modulated by factors in serum.
Collapse
Affiliation(s)
- A J Franklin
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee 37232
| | | | | | | |
Collapse
|
21
|
Human GATA-3 trans-activation, DNA-binding, and nuclear localization activities are organized into distinct structural domains. Mol Cell Biol 1994. [PMID: 8114750 DOI: 10.1128/mcb.14.3.2201] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
GATA-3 is a zinc finger transcription factor which is expressed in a highly restricted and strongly conserved tissue distribution pattern in vertebrate organisms, specifically, in a subset of hematopoietic cells, in cells within the central and peripheral nervous systems, in the kidney, and in placental trophoblasts. Tissue-specific cellular genes regulated by GATA-3 have been identified in T lymphocytes and the placenta, while GATA-3-regulated genes in the nervous system and kidney have not yet been defined. We prepared monoclonal antibodies with which we could dissect the biochemical and functional properties of human GATA-3. The results of these experiments show some anticipated phenotypes, for example, the definition of discrete domains required for specific DNA-binding site recognition (amino acids 303 to 348) and trans activation (amino acids 30 to 74). The signaling sequence for nuclear localization of human GATA-3 is a property conferred by sequences within and surrounding the amino finger (amino acids 249 to 311) of the protein, thereby assigning a function to this domain and thus explaining the curious observation that this zinc finger is dispensable for DNA binding by the GATA family of transcription factors.
Collapse
|
22
|
Yang Z, Gu L, Romeo PH, Bories D, Motohashi H, Yamamoto M, Engel JD. Human GATA-3 trans-activation, DNA-binding, and nuclear localization activities are organized into distinct structural domains. Mol Cell Biol 1994; 14:2201-12. [PMID: 8114750 PMCID: PMC358580 DOI: 10.1128/mcb.14.3.2201-2212.1994] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
GATA-3 is a zinc finger transcription factor which is expressed in a highly restricted and strongly conserved tissue distribution pattern in vertebrate organisms, specifically, in a subset of hematopoietic cells, in cells within the central and peripheral nervous systems, in the kidney, and in placental trophoblasts. Tissue-specific cellular genes regulated by GATA-3 have been identified in T lymphocytes and the placenta, while GATA-3-regulated genes in the nervous system and kidney have not yet been defined. We prepared monoclonal antibodies with which we could dissect the biochemical and functional properties of human GATA-3. The results of these experiments show some anticipated phenotypes, for example, the definition of discrete domains required for specific DNA-binding site recognition (amino acids 303 to 348) and trans activation (amino acids 30 to 74). The signaling sequence for nuclear localization of human GATA-3 is a property conferred by sequences within and surrounding the amino finger (amino acids 249 to 311) of the protein, thereby assigning a function to this domain and thus explaining the curious observation that this zinc finger is dispensable for DNA binding by the GATA family of transcription factors.
Collapse
Affiliation(s)
- Z Yang
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500
| | | | | | | | | | | | | |
Collapse
|
23
|
Serum factors can modulate the developmental clock of gamma- to beta-globin gene switching in somatic cell hybrids. Mol Cell Biol 1993. [PMID: 8336721 DOI: 10.1128/mcb.13.8.4844] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The fusion of human fetal erythroid (HFE) cells with mouse erythroleukemia (MEL) cells produces stable synkaryons (HFE x MEL) which can be monitored for extended periods of time in culture. Initially these hybrids express a human fetal globin program (gamma >> beta), but after weeks or months in culture, they switch to an adult pattern of globin expression (beta >> gamma). The rate at which hybrids switch to the adult phenotype is roughly dependent on the gestational age of the fetal erythroid cells used in the fusion, suggesting that the rate of switching in vitro may be determined by a developmental clock type of mechanism, possibly involving the cumulative number of divisions experienced by the human fetal cells. To investigate whether the number or rate of cell divisions postfusion can influence the rate of switching, we monitored the rate of switching in hybrids from independent fusions under growth-promoting (serum-replete) and growth-suppressing (serum-deprived) conditions. We found that hybrids grown under serum-deprived or serumless conditions switched more rapidly to adult globin expression than did their counterparts in serum-replete conditions. Neither the number of cumulative cell divisions nor time in culture per se predicted the rate of switching in vitro. Our data suggest that factors present in serum either retard switching of hybrids by their presence or promote switching by their absence, indicating that globin switching in vitro can be modulated by the environment; however, once switching in HFE x MEL hybrids is complete, serum factors cannot reverse this process.
Collapse
|
24
|
Zitnik G, Li Q, Stamatoyannopoulos G, Papayannopoulou T. Serum factors can modulate the developmental clock of gamma- to beta-globin gene switching in somatic cell hybrids. Mol Cell Biol 1993; 13:4844-51. [PMID: 8336721 PMCID: PMC360113 DOI: 10.1128/mcb.13.8.4844-4851.1993] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The fusion of human fetal erythroid (HFE) cells with mouse erythroleukemia (MEL) cells produces stable synkaryons (HFE x MEL) which can be monitored for extended periods of time in culture. Initially these hybrids express a human fetal globin program (gamma >> beta), but after weeks or months in culture, they switch to an adult pattern of globin expression (beta >> gamma). The rate at which hybrids switch to the adult phenotype is roughly dependent on the gestational age of the fetal erythroid cells used in the fusion, suggesting that the rate of switching in vitro may be determined by a developmental clock type of mechanism, possibly involving the cumulative number of divisions experienced by the human fetal cells. To investigate whether the number or rate of cell divisions postfusion can influence the rate of switching, we monitored the rate of switching in hybrids from independent fusions under growth-promoting (serum-replete) and growth-suppressing (serum-deprived) conditions. We found that hybrids grown under serum-deprived or serumless conditions switched more rapidly to adult globin expression than did their counterparts in serum-replete conditions. Neither the number of cumulative cell divisions nor time in culture per se predicted the rate of switching in vitro. Our data suggest that factors present in serum either retard switching of hybrids by their presence or promote switching by their absence, indicating that globin switching in vitro can be modulated by the environment; however, once switching in HFE x MEL hybrids is complete, serum factors cannot reverse this process.
Collapse
Affiliation(s)
- G Zitnik
- Department of Medicine, University of Washington, Seattle 98195
| | | | | | | |
Collapse
|