1
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Minocha S, Herr W. Cortical and Commissural Defects Upon HCF-1 Loss in Nkx2.1-Derived Embryonic Neurons and Glia. Dev Neurobiol 2019; 79:578-595. [PMID: 31207118 PMCID: PMC6771735 DOI: 10.1002/dneu.22704] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 06/06/2019] [Accepted: 06/06/2019] [Indexed: 11/28/2022]
Abstract
Formation of the cerebral cortex and commissures involves a complex developmental process defined by multiple molecular mechanisms governing proliferation of neuronal and glial precursors, neuronal and glial migration, and patterning events. Failure in any of these processes can lead to malformations. Here, we study the role of HCF-1 in these processes. HCF-1 is a conserved metazoan transcriptional co-regulator long implicated in cell proliferation and more recently in human metabolic disorders and mental retardation. Loss of HCF-1 in a subset of ventral telencephalic Nkx2.1-positive progenitors leads to reduced numbers of GABAergic interneurons and glia, owing not to decreased proliferation but rather to increased apoptosis before cell migration. The loss of these cells leads to development of severe commissural and cortical defects in early postnatal mouse brains. These defects include mild and severe structural defects of the corpus callosum and anterior commissure, respectively, and increased folding of the cortex resembling polymicrogyria. Hence, in addition to its well-established role in cell proliferation, HCF-1 is important for organ development, here the brain.
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Affiliation(s)
- Shilpi Minocha
- Center for Integrative Genomics, GénopodeUniversity of LausanneLausanneCH‐1015Switzerland
| | - Winship Herr
- Center for Integrative Genomics, GénopodeUniversity of LausanneLausanneCH‐1015Switzerland
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2
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Epiblast-specific loss of HCF-1 leads to failure in anterior-posterior axis specification. Dev Biol 2016; 418:75-88. [PMID: 27521049 DOI: 10.1016/j.ydbio.2016.08.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 08/08/2016] [Accepted: 08/08/2016] [Indexed: 02/06/2023]
Abstract
Mammalian Host-Cell Factor 1 (HCF-1), a transcriptional co-regulator, plays important roles during the cell-division cycle in cell culture, embryogenesis as well as adult tissue. In mice, HCF-1 is encoded by the X-chromosome-linked Hcfc1 gene. Induced Hcfc1(cKO/+) heterozygosity with a conditional knockout (cKO) allele in the epiblast of female embryos leads to a mixture of HCF-1-positive and -deficient cells owing to random X-chromosome inactivation. These embryos survive owing to the replacement of all HCF-1-deficient cells by HCF-1-positive cells during E5.5 to E8.5 of development. In contrast, complete epiblast-specific loss of HCF-1 in male embryos, Hcfc1(epiKO/Y), leads to embryonic lethality. Here, we characterize this lethality. We show that male epiblast-specific loss of Hcfc1 leads to a developmental arrest at E6.5 with a rapid progressive cell-cycle exit and an associated failure of anterior visceral endoderm migration and primitive streak formation. Subsequently, gastrulation does not take place. We note that the pattern of Hcfc1(epiKO/Y) lethality displays many similarities to loss of β-catenin function. These results reveal essential new roles for HCF-1 in early embryonic cell proliferation and development.
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3
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Minocha S, Sung TL, Villeneuve D, Lammers F, Herr W. Compensatory embryonic response to allele-specific inactivation of the murine X-linked gene Hcfc1. Dev Biol 2016; 412:1-17. [DOI: 10.1016/j.ydbio.2016.02.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 02/22/2016] [Accepted: 02/22/2016] [Indexed: 01/29/2023]
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4
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Huang L, Jolly LA, Willis-Owen S, Gardner A, Kumar R, Douglas E, Shoubridge C, Wieczorek D, Tzschach A, Cohen M, Hackett A, Field M, Froyen G, Hu H, Haas SA, Ropers HH, Kalscheuer VM, Corbett MA, Gecz J. A noncoding, regulatory mutation implicates HCFC1 in nonsyndromic intellectual disability. Am J Hum Genet 2012; 91:694-702. [PMID: 23000143 DOI: 10.1016/j.ajhg.2012.08.011] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Revised: 06/26/2012] [Accepted: 08/13/2012] [Indexed: 11/28/2022] Open
Abstract
The discovery of mutations causing human disease has so far been biased toward protein-coding regions. Having excluded all annotated coding regions, we performed targeted massively parallel resequencing of the nonrepetitive genomic linkage interval at Xq28 of family MRX3. We identified in the binding site of transcription factor YY1 a regulatory mutation that leads to overexpression of the chromatin-associated transcriptional regulator HCFC1. When tested on embryonic murine neural stem cells and embryonic hippocampal neurons, HCFC1 overexpression led to a significant increase of the production of astrocytes and a considerable reduction in neurite growth. Two other nonsynonymous, potentially deleterious changes have been identified by X-exome sequencing in individuals with intellectual disability, implicating HCFC1 in normal brain function.
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Affiliation(s)
- Lingli Huang
- Genetics and Molecular Pathology, SA Pathology, North Adelaide, SA 5006, Australia
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5
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Wysocka J, Herr W. The herpes simplex virus VP16-induced complex: the makings of a regulatory switch. Trends Biochem Sci 2003; 28:294-304. [PMID: 12826401 DOI: 10.1016/s0968-0004(03)00088-4] [Citation(s) in RCA: 226] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
When herpes simplex virus (HSV) infects human cells, it is able to enter two modes of infection: lytic and latent. A key activator of lytic infection is a virion protein called VP16, which, upon infection of a permissive cell, forms a transcriptional regulatory complex with two cellular proteins - the POU-domain transcription factor Oct-1 and the cell-proliferation factor HCF-1 - to activate transcription of the first set of expressed viral genes. This regulatory complex, called the VP16-induced complex, reveals mechanisms of combinatorial control of transcription. The activities of Oct-1 and HCF-1 - two important regulators of cellular gene expression and proliferation - illuminate strategies by which HSV might coexist with its host.
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6
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Julien E, Herr W. Proteolytic processing is necessary to separate and ensure proper cell growth and cytokinesis functions of HCF-1. EMBO J 2003; 22:2360-9. [PMID: 12743030 PMCID: PMC156000 DOI: 10.1093/emboj/cdg242] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
HCF-1 is a highly conserved and abundant chromatin-associated host cell factor required for transcriptional activation of herpes simplex virus immediate-early genes by the virion protein VP16. HCF-1 exists as a heterodimeric complex of associated N- (HCF-1(N)) and C- (HCF-1(C)) terminal subunits that result from proteolytic processing of a precursor protein. We have used small-interfering RNA (siRNA) to inactivate HCF-1 in an array of normal and transformed mammalian cells to identify its cellular functions. Our results show that HCF-1 is a broadly acting regulator of two stages of the cell cycle: exit from mitosis, where it ensures proper cytokinesis, and passage through the G(1) phase, where it promotes cell cycle progression. Proteolytic processing is necessary to separate and ensure these two HCF-1 activities, which are performed by separate HCF-1 subunits: the HCF-1(N) subunit promotes passage through the G(1) phase whereas the HCF-1(C) subunit is involved in proper exit from mitosis. These results suggest that HCF-1 links the regulation of exit from mitosis and the G(1) phase of cell growth, possibly to coordinate the reactivation of gene expression after mitosis.
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Affiliation(s)
- Eric Julien
- Cold Spring Harbor Laboratory, NY 11724, USA
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7
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Wysocka J, Myers MP, Laherty CD, Eisenman RN, Herr W. Human Sin3 deacetylase and trithorax-related Set1/Ash2 histone H3-K4 methyltransferase are tethered together selectively by the cell-proliferation factor HCF-1. Genes Dev 2003; 17:896-911. [PMID: 12670868 PMCID: PMC196026 DOI: 10.1101/gad.252103] [Citation(s) in RCA: 314] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The abundant and chromatin-associated protein HCF-1 is a critical player in mammalian cell proliferation as well as herpes simplex virus (HSV) transcription. We show here that separate regions of HCF-1 critical for its role in cell proliferation associate with the Sin3 histone deacetylase (HDAC) and a previously uncharacterized human trithorax-related Set1/Ash2 histone methyltransferase (HMT). The Set1/Ash2 HMT methylates histone H3 at Lys 4 (K4), but not if the neighboring K9 residue is already methylated. HCF-1 tethers the Sin3 and Set1/Ash2 transcriptional regulatory complexes together even though they are generally associated with opposite transcriptional outcomes: repression and activation of transcription, respectively. Nevertheless, this tethering is context-dependent because the transcriptional activator VP16 selectively binds HCF-1 associated with the Set1/Ash2 HMT complex in the absence of the Sin3 HDAC complex. These results suggest that HCF-1 can broadly regulate transcription, both positively and negatively, through selective modulation of chromatin structure.
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Affiliation(s)
- Joanna Wysocka
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
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8
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Ajuh P, Chusainow J, Ryder U, Lamond AI. A novel function for human factor C1 (HCF-1), a host protein required for herpes simplex virus infection, in pre-mRNA splicing. EMBO J 2002; 21:6590-602. [PMID: 12456665 PMCID: PMC136956 DOI: 10.1093/emboj/cdf652] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Human factor C1 (HCF-1) is needed for the expression of herpes simplex virus 1 (HSV-1) immediate-early genes in infected mammalian cells. Here, we provide evidence that HCF-1 is required for spliceosome assembly and splicing in mammalian nuclear extracts. HCF-1 interacts with complexes containing splicing snRNPs in uninfected mammalian cells and is a stable component of the spliceosome complex. We show that a missense mutation in HCF-1 in the BHK21 hamster cell line tsBN67, at the non-permissive temperature, inhibits the protein's interaction with U1 and U5 splicing snRNPs, causes inefficient spliceosome assembly and inhibits splicing. Transient expression of wild-type HCF-1 in tsBN67 cells restores splicing at the non-permissive temperature. The inhibition of splicing in tsBN67 cells correlates with the temperature-sensitive cell cycle arrest phenotype, suggesting that HCF-1-dependent splicing events may be required for cell cycle progression.
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Affiliation(s)
| | | | | | - Angus I. Lamond
- School of Life Sciences, The University of Dundee, Dow Street, Dundee DD1 5EH, UK
Corresponding author e-mail:
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9
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Piluso D, Bilan P, Capone JP. Host cell factor-1 interacts with and antagonizes transactivation by the cell cycle regulatory factor Miz-1. J Biol Chem 2002; 277:46799-808. [PMID: 12244100 DOI: 10.1074/jbc.m206226200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Human host cell factor-1 (HCF-1) is essential for cell cycle progression and is required, in conjunction with the herpes simplex virus transactivator VP16, for induction of viral immediate-early gene expression. We show here that HCF-1 directly binds to the Myc-interacting protein Miz-1, a transcription factor that induces cell cycle arrest at G(1), in part by directly stimulating expression of the cyclin-dependent kinase inhibitor p15(INK4b). A domain encompassing amino acids 750-836, contained within a subregion of HCF-1 required for cell cycle progression, was sufficient to bind Miz-1. Conversely, HCF-1 interacted with two separate regions in Miz-1: the N-terminal POZ domain and a C-terminal domain (residues 637-803) previously shown to harbor determinants for interaction with c-Myc and the coactivator p300. The latter functioned as a potent transactivation domain when tethered to DNA, indicating that HCF-1 targets a transactivation function in Miz-1. HCF-1 or a Miz-1-binding fragment of HCF-1 repressed transactivation by Gal4-Miz-1 in transfection assays. Moreover, HCF-1 repressed Miz-1-mediated transactivation of a reporter gene linked to the p15(INK4b) promoter. Protein/protein interaction studies and transient transfection assays demonstrated that HCF-1 interferes with recruitment of p300 to Miz-1, similar to what has been reported with c-Myc. Our findings identify Miz-1 as a novel HCF-1-interacting partner and illustrate cross-talk between these two proteins that may be of consequence to their respective functions in gene regulation and their opposing effects on the cell cycle.
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Affiliation(s)
- David Piluso
- Department of Biochemistry, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
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10
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Vogel JL, Kristie TM. Autocatalytic proteolysis of the transcription factor-coactivator C1 (HCF): a potential role for proteolytic regulation of coactivator function. Proc Natl Acad Sci U S A 2000; 97:9425-30. [PMID: 10920196 PMCID: PMC16880 DOI: 10.1073/pnas.160266697] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Site-specific proteolysis is an important biological mechanism for the regulation of cellular processes such as gene expression, cell signaling, development, and apoptosis. In transcriptional regulation, specific proteolysis regulates the localization and activity of many regulatory factors. The C1 factor (HCF), a cellular transcription factor and coactivator, undergoes site-specific proteolytic processing at a series of unusual amino acid reiterations to generate a family of amino- and carboxyl-terminal polypeptides that remain tightly associated. Expression and purification of bacterially expressed domains of the C1 factor identifies an autocatalytic activity that is responsible for the specific cleavage of the reiterations. In addition, coexpression of the autocatalytic domain with a heterologous protein containing a target cleavage site demonstrates that the C1 protease may also function in trans.
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Affiliation(s)
- J L Vogel
- Laboratory of Viral Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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11
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Lu R, Misra V. Zhangfei: a second cellular protein interacts with herpes simplex virus accessory factor HCF in a manner similar to Luman and VP16. Nucleic Acids Res 2000; 28:2446-54. [PMID: 10871379 PMCID: PMC102720 DOI: 10.1093/nar/28.12.2446] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Host cell factor (HCF, C1, VCAF or CFF) is a cellular protein that is required for transcription activation of herpes simplex virus (HSV) immediate-early (IE) genes by the virion protein VP16. The biological function of HCF remains unclear. Recently we identified a cellular transcription activator, Luman. As with VP16, the transactivation function of Luman is also regulated by HCF. Here we report a second human protein, Zhangfei (ZF) that interacts with HCF in a fashion similar to Luman and VP16. Although ZF shares no significant sequence homology with Luman, the two proteins have some structural similarities. These include: a basic domain-leucine zipper (bZIP) region, an acidic activation domain and a consensus HCF-binding motif. Unlike Luman, or most other bZIP proteins, ZF by itself did not appear to bind consensus bZIP-binding sites. It was also unable to activate promoters containing these response elements. Although in transient expression assays ectopically expressed ZF was unable to block transactivation by VP16 of a HSV IE promoter, ZF could prevent the expression of several HSV proteins in cells infected with the virus. The ability of ZF to block the synthesis of the HSV IE protein ICP0 relied on its binding to HCF, since a mutant of ZF that was unable to bind HCF was also unable to prevent viral IE protein expression.
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Affiliation(s)
- R Lu
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan S7N 5B4, Canada
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12
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Jin DY, Wang HL, Zhou Y, Chun AC, Kibler KV, Hou YD, Kung H, Jeang KT. Hepatitis C virus core protein-induced loss of LZIP function correlates with cellular transformation. EMBO J 2000; 19:729-40. [PMID: 10675342 PMCID: PMC305611 DOI: 10.1093/emboj/19.4.729] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Hepatitis C virus (HCV) is the major etiological agent of blood-borne non-A non-B hepatitis and a leading cause of liver cirrhosis and hepatocellular carcinoma worldwide. HCV core protein is a multifunctional protein with regulatory functions in cellular transcription and virus-induced transformation and pathogenesis. Here we report on the identification of a bZIP nuclear transcription protein as an HCV core cofactor for transformation. This bZIP factor, designated LZIP, activates CRE-dependent transcription and regulates cell proliferation. Loss of LZIP function in NIH 3T3 cells triggers morphological transformation and anchorage-independent growth. We show that HCV core protein aberrantly sequesters LZIP in the cytoplasm, inactivates LZIP function and potentiates cellular transformation. Our findings suggest that LZIP might serve a novel cellular tumor suppressor function that is targeted by the HCV core.
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Affiliation(s)
- D Y Jin
- Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-0460, USA.
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13
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Ajuh PM, Browne GJ, Hawkes NA, Cohen PT, Roberts SG, Lamond AI. Association of a protein phosphatase 1 activity with the human factor C1 (HCF) complex. Nucleic Acids Res 2000; 28:678-86. [PMID: 10637318 PMCID: PMC102561 DOI: 10.1093/nar/28.3.678] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We have screened a human cDNA expression library with a digoxygenin-labelled protein phosphatase 1 (PP1) probe to identify novel PP1 interacting proteins. Eleven cDNA clones were isolated, which included genes encoding two previously characterised and six novel PP1 binding proteins. Three of the cDNAs encoded a protein called host cell factor (HCF), which is an essential component of the cellular complex required for the transcription of the herpes simplex virus (HSV) immediate-early (IE) genes. We demonstrate that HCF and PP1 exist as a complex in nuclear extracts and that this complex is distinct from the form of HCF that associates with HSV VP16. The data suggest novel roles for HCF and PP1, which may be relevant to their functions in transcription and cell cycle progression.
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Affiliation(s)
- P M Ajuh
- Department of Biochemistry, The University of Dundee, MSI/WTB Complex, Dow Street, Dundee DD1 5EH, UK
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14
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Herr W. The herpes simplex virus VP16-induced complex: mechanisms of combinatorial transcriptional regulation. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 1999; 63:599-607. [PMID: 10384325 DOI: 10.1101/sqb.1998.63.599] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- W Herr
- Cold Spring Harbor Laboratory, New York 11724, USA
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15
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Johnson KM, Mahajan SS, Wilson AC. Herpes simplex virus transactivator VP16 discriminates between HCF-1 and a novel family member, HCF-2. J Virol 1999; 73:3930-40. [PMID: 10196288 PMCID: PMC104171 DOI: 10.1128/jvi.73.5.3930-3940.1999] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Herpes simplex virus infection is initiated by VP16, a viral transcription factor that activates the viral immediate-early (IE) genes. VP16 does not recognize the IE gene promoters directly but instead forms a multiprotein complex with Oct-1 and HCF-1, a ubiquitous nuclear protein required for progression through the G1 phase of the cell cycle. The functional significance of recruiting HCF-1 to the VP16-induced complex is not understood. Here we describe the identification of a second HCF-like protein, designated HCF-2. HCF-2 is smaller than HCF-1 but shares three regions of strong amino acid sequence homology, including the beta-propeller domain required for association with VP16. HCF-2 is expressed in many tissues, especially the testis, and shows a more dynamic pattern of subcellular localization than HCF-1. Although HCF-2 associates with VP16 and can support complex assembly with Oct-1 and DNA, it is significantly less efficient than HCF-1. A similar preference is shown by LZIP, a cellular counterpart of VP16. Analysis of chimeric proteins showed that differences between the fifth and sixth kelch repeats of the beta-propeller domains from HCF-1 and HCF-2 dictate this selectivity. These results reveal an unexpected level of specificity in the recruitment of HCF-1 to the VP16-induced complex, paralleling the preferential selection of Oct-1 rather than the closely related POU domain protein Oct-2. Implications for regulation of the viral life cycle are discussed.
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Affiliation(s)
- K M Johnson
- Department of Microbiology and Kaplan Comprehensive Cancer Center, New York University Medical Center, New York, New York 10016, USA
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16
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Kristie TM, Vogel JL, Sears AE. Nuclear localization of the C1 factor (host cell factor) in sensory neurons correlates with reactivation of herpes simplex virus from latency. Proc Natl Acad Sci U S A 1999; 96:1229-33. [PMID: 9990006 PMCID: PMC15445 DOI: 10.1073/pnas.96.4.1229] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
After a primary infection, herpes simplex virus is maintained in a latent state in neurons of sensory ganglia until complex stimuli reactivate viral lytic replication. Although the mechanisms governing reactivation from the latent state remain unknown, the regulated expression of the viral immediate early genes represents a critical point in this process. These genes are controlled by transcription enhancer complexes whose assembly requires and is coordinated by the cellular C1 factor (host cell factor). In contrast to other tissues, the C1 factor is not detected in the nuclei of sensory neurons. Experimental conditions that induce the reactivation of herpes simplex virus in mouse model systems result in rapid nuclear localization of the protein, indicating that the C1 factor is sequestered in these cells until reactivation signals induce a redistribution of the protein. The regulated localization suggests that C1 is a critical switch determinant of the viral lytic-latent cycle.
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Affiliation(s)
- T M Kristie
- Laboratory of Viral Diseases, National Institutes of Health, Building 4-133, 9000, Rockville Pike, Bethesda, MD 20892, USA.
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17
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Liu Y, Hengartner MO, Herr W. Selected elements of herpes simplex virus accessory factor HCF are highly conserved in Caenorhabditis elegans. Mol Cell Biol 1999; 19:909-15. [PMID: 9858614 PMCID: PMC83948 DOI: 10.1128/mcb.19.1.909] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/1998] [Accepted: 10/07/1998] [Indexed: 11/20/2022] Open
Abstract
HCF is a mammalian nuclear protein that undergoes proteolytic processing and is required for cell proliferation. During productive herpes simplex virus (HSV) infection, the viral transactivator VP16 associates with HCF to initiate HSV gene transcription. Here, we show that the worm Caenorhabditis elegans possesses a functional homolog of mammalian HCF that can associate with and activate the viral protein VP16. The pattern of sequence conservation, however, is uneven. Sequences required for mammalian HCF processing are not present in C. elegans HCF. Furthermore, not all elements of mammalian HCF that are required for promoting cell proliferation are conserved. Nevertheless, unexpectedly, C. elegans HCF can promote mammalian cell proliferation because a region of HCF that is conserved can promote mammalian cell proliferation better than its human counterpart. These results suggest that HCF possesses a highly conserved role in metazoan cell proliferation which is targeted by VP16 to regulate HSV infection. The precise mechanisms, however, by which HCF functions in mammals and worms appear to differ.
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Affiliation(s)
- Y Liu
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
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18
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Lu R, Yang P, Padmakumar S, Misra V. The herpesvirus transactivator VP16 mimics a human basic domain leucine zipper protein, luman, in its interaction with HCF. J Virol 1998; 72:6291-7. [PMID: 9658067 PMCID: PMC109766 DOI: 10.1128/jvi.72.8.6291-6297.1998] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
In human cells infected with herpes simplex virus (HSV), viral gene expression is initiated by the virion protein VP16. VP16 does not bind DNA directly but forms a multiprotein complex on the viral immediate-early gene promoters with two cellular proteins: the POU domain protein Oct-1 and host cell factor (HCF; also called C1, VCAF, and CFF). Despite its apparent role in stabilizing the VP16-induced transcription complex, the natural biological role of HCF is unclear. Only recently HCF has been implicated in control of the cell cycle. To determine the role of HCF in cells and answer why HSV has evolved an HCF-dependent mechanism for the initiation of the lytic cycle, we identified the first human ligand for HCF (R. Lu et al., Mol. Cell. Biol. 17:5117-5126, 1997). This protein, Luman, is a member of the CREB/ATF family of transcription factors that can activate transcription from promoters containing cyclic AMP response elements (CRE). Here we provide evidence that Luman and VP16 share two important structural features: an acidic activation domain and a common mechanism for binding HCF. We found that Luman, its homolog in Drosophila, dCREB-A (also known as BBF-2), and VP16 bind to HCF by a motif, (D/E)HXY(S/A), present in all three proteins. In addition, a mutation (P134S) in HCF that prevents VP16 binding also abolishes its binding to Luman and dCREB-A. We also show that while interaction with HCF is not required for the ability of Luman to activate transcription when tethered to the GAL4 promoter, it appears to be essential for Luman to activate transcription through CRE sites. These data suggest that the HCF-Luman interaction may represent a conserved mechanism for transcriptional regulation in metazoans, and HSV mimics this interaction with HCF to monitor the physiological state of the host cell.
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Affiliation(s)
- R Lu
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B4
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