1
|
Doshi J, Willis K, Madurga A, Stelzer C, Benenson Y. Multiple Alternative Promoters and Alternative Splicing Enable Universal Transcription-Based Logic Computation in Mammalian Cells. Cell Rep 2020; 33:108437. [PMID: 33264624 DOI: 10.1016/j.celrep.2020.108437] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 09/04/2020] [Accepted: 11/05/2020] [Indexed: 10/22/2022] Open
Abstract
Multi-input logic gene circuits can enable sophisticated control of cell function, yet large-scale synthetic circuitry in mammalian cells has relied on post-transcriptional regulation or recombinase-triggered state transitions. Large-scale transcriptional logic, on the other hand, has been challenging to implement. Inspired by a naturally found regulatory strategy of using multiple alternative promoters, followed by alternative splicing, we developed a scalable and compact platform for transcriptional OR logic using inputs to those promoters. The platform is extended to implement disjunctive normal form (DNF) computations capable of implementing arbitrary logic rules. Specifically, AND logic is implemented at individual promoters using synergistic transcriptional inputs, and NOT logic via microRNA inputs targeting unique exon sequences driven by those promoters. Together, these regulatory programs result in DNF-like logic control of output gene expression. The approach offers flexibility for building complex logic programs in mammalian cells.
Collapse
Affiliation(s)
- Jiten Doshi
- Department of Biosystems Science and Engineering, ETH Zurich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Katie Willis
- Department of Biosystems Science and Engineering, ETH Zurich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Angela Madurga
- Department of Biosystems Science and Engineering, ETH Zurich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Christoph Stelzer
- Department of Biosystems Science and Engineering, ETH Zurich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Yaakov Benenson
- Department of Biosystems Science and Engineering, ETH Zurich, Mattenstrasse 26, 4058 Basel, Switzerland.
| |
Collapse
|
2
|
Han J, Tam K, Ma F, Tam C, Aleshe B, Wang X, Quintos JP, Morselli M, Pellegrini M, Hollis RP, Kohn DB. β-Globin Lentiviral Vectors Have Reduced Titers due to Incomplete Vector RNA Genomes and Lowered Virion Production. Stem Cell Reports 2020; 16:198-211. [PMID: 33186538 PMCID: PMC7897704 DOI: 10.1016/j.stemcr.2020.10.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 10/15/2020] [Accepted: 10/16/2020] [Indexed: 12/29/2022] Open
Abstract
Lentiviral vectors (LVs) commonly used for the treatment of hemoglobinopathies often have low titers and sub-optimal gene transfer efficiency for human hematopoietic stem and progenitor cells (HSPCs), hindering clinical translation and commercialization for ex vivo gene therapy. We observed that a high percentage of β-globin LV viral genomic RNAs were incomplete toward the 3′ end in packaging cells and in released vector particles. The incomplete vector genomes impeded reverse transcription in target cells, limiting stable gene transfer to HSPCs. By combining three modifications to vector design and production (shortening the vector length to 5.3 kb; expressing HIV-1 Tat protein during packaging; and packaging in PKR−/− cells) there was a 30-fold increase in vector titer and a 3-fold increase in vector infectivity in HSPCs. These approaches may improve the manufacturing of β-globin and other complex LVs for enhanced gene delivery and may facilitate clinical applications. Vector genomes are truncated in a length-dependent manner during packaging Truncated RNAs cannot be reverse transcribed, impeding titer and infectivity Protein kinase R inhibits virion formation for bidirectional lentiviral vectors Three strategies to improve lentiviral vector titer by 30× and infectivity by 3×
Collapse
Affiliation(s)
- Jiaying Han
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Terasaki Life Sciences Building, 610 Charles E. Young Drive East, Los Angeles, CA 90095-1489, USA
| | - Kevin Tam
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, USA
| | - Feiyang Ma
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, USA
| | - Curtis Tam
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, USA
| | - Bamidele Aleshe
- Department of Microbiology, Immunology & Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, USA
| | - Xiaoyan Wang
- Department of General Internal Medicine and Health Services Research, UCLA, Los Angeles, CA, USA
| | - Jason P Quintos
- Department of Microbiology, Immunology & Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, USA
| | - Marco Morselli
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, USA
| | - Matteo Pellegrini
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, USA
| | - Roger P Hollis
- Department of Microbiology, Immunology & Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, USA
| | - Donald B Kohn
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Terasaki Life Sciences Building, 610 Charles E. Young Drive East, Los Angeles, CA 90095-1489, USA; Department of Microbiology, Immunology & Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, USA; Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, USA; The Eli & Edythe Broad Center of Regenerative Medicine & Stem Cell Research, University of California, Los Angeles, USA; UCLA Jonsson Comprehensive Cancer Center, Los Angeles, USA.
| |
Collapse
|
3
|
Choi SH, Reeves RE, Romano Ibarra GS, Lynch TJ, Shahin WS, Feng Z, Gasser GN, Winter MC, Evans TIA, Liu X, Luo M, Zhang Y, Stoltz DA, Devor EJ, Yan Z, Engelhardt JF. Detargeting Lentiviral-Mediated CFTR Expression in Airway Basal Cells Using miR-106b. Genes (Basel) 2020; 11:E1169. [PMID: 33036232 PMCID: PMC7601932 DOI: 10.3390/genes11101169] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Revised: 09/29/2020] [Accepted: 10/02/2020] [Indexed: 12/12/2022] Open
Abstract
Lentiviral-mediated integration of a CFTR transgene cassette into airway basal cells is a strategy being considered for cystic fibrosis (CF) cell-based therapies. However, CFTR expression is highly regulated in differentiated airway cell types and a subset of intermediate basal cells destined to differentiate. Since basal stem cells typically do not express CFTR, suppressing the CFTR expression from the lentiviral vector in airway basal cells may be beneficial for maintaining their proliferative capacity and multipotency. We identified miR-106b as highly expressed in proliferating airway basal cells and extinguished in differentiated columnar cells. Herein, we developed lentiviral vectors with the miR-106b-target sequence (miRT) to both study miR-106b regulation during basal cell differentiation and detarget CFTR expression in basal cells. Given that miR-106b is expressed in the 293T cells used for viral production, obstacles of viral genome integrity and titers were overcome by creating a 293T-B2 cell line that inducibly expresses the RNAi suppressor B2 protein from flock house virus. While miR-106b vectors effectively detargeted reporter gene expression in proliferating basal cells and following differentiation in the air-liquid interface and organoid cultures, the CFTR-miRT vector produced significantly less CFTR-mediated current than the non-miR-targeted CFTR vector following transduction and differentiation of CF basal cells. These findings suggest that miR-106b is expressed in certain airway cell types that contribute to the majority of CFTR anion transport in airway epithelium.
Collapse
Affiliation(s)
- Soon H. Choi
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| | - Rosie E. Reeves
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| | | | - Thomas J. Lynch
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| | - Weam S. Shahin
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| | - Zehua Feng
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| | - Grace N. Gasser
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| | - Michael C. Winter
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| | - T. Idil Apak Evans
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| | - Xiaoming Liu
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| | - Meihui Luo
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| | - Yulong Zhang
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| | - David A. Stoltz
- Department of Internal Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA 52246, USA;
| | - Eric J. Devor
- Department of Obstetrics and Gynecology, University of Iowa, Carver College of Medicine, Iowa City, IA 52246, USA;
| | - Ziying Yan
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| | - John F. Engelhardt
- Department of Anatomy and Cell Biology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA; (S.H.C.); (R.E.R.); (T.J.L.); (W.S.S.); (Z.F.); (G.N.G.); (M.C.W.); (T.I.A.E.); (X.L.); (M.L.); (Y.Z.); (Z.Y.)
| |
Collapse
|
4
|
Zhang Y, Chen D, Zhang G, Wu X, Zhou L, Lin Y, Ding J, An F, Zhan Q. MicroRNA-23b-3p promotes pancreatic cancer cell tumorigenesis and metastasis via the JAK/PI3K and Akt/NF-κB signaling pathways. Oncol Lett 2020; 20:160. [PMID: 32934728 PMCID: PMC7471709 DOI: 10.3892/ol.2020.12021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 06/29/2020] [Indexed: 02/06/2023] Open
Abstract
MicroRNA (miR)-23b-3p plays an important role in tumor growth, proliferation, invasion and migration in pancreatic cancer (PC). However, the function and mechanistic role of miR-23b-3p in the development of PC remains largely unknown. In the present study, the miR-23b-3p levels in the serum of patients with PC were found to be elevated, and the phosphorylation levels of Janus kinase (JAK)2, PI3K, Akt and NF-κВ were found to be upregulated. In addition, miR-23b-3p was induced in response to interleukin-6 (IL-6), which is known to be involved in the progression of PC. Overexpression of miR-23b-3p, on the other hand, activated the JAK/PI3K and Akt/NF-κB signaling pathways in PC cells, as evidenced by miR-23b-3p-induced upregulation of phosphorylated (p-)JAK2, p-PI3K, p-Akt and p-NF-κВ, as well as the downregulation of PTEN; and these effects were found to be reversible by miR-23b-3p inhibition. Furthermore, miR-23b-3p was found to downregulate PTEN by directly targeting the 3′-untranslated region of PTEN mRNA. Notably, in an in vivo xenograft mouse model, overexpression of miR-23b-3p accelerated PC cell-derived tumor growth, activated the JAK/Akt/NF-κВ signaling pathway and promoted liver metastasis. In contrast, knockdown of miR-23b-3p suppressed tumor growth and metastasis as well as JAK/Akt/NF-κВ signaling activity. In vivo imaging of the mice further confirmed the metastasis promoting role of miR-23b-3p in PC. These results suggested that miR-23b-3p enhances PC cell tumorigenesis and metastasis, at least, partially via the JAK/PI3K and Akt/NF-κB signaling pathways. Therefore, targeting miR-23b-3p or the JAK/PI3K and Akt/NF-κB signalings may be potential therapeutic strategy against PC.
Collapse
Affiliation(s)
- Yunan Zhang
- Department of Gastroenterology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Dayang Chen
- Department of Gastroenterology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Guoqiang Zhang
- Department of Gastroenterology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Xiongbo Wu
- Department of Gastroenterology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Liangyun Zhou
- Department of Gastroenterology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Yexin Lin
- Department of Gastroenterology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Junli Ding
- Department of Oncology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Fangmei An
- Department of Gastroenterology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Qiang Zhan
- Department of Gastroenterology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| |
Collapse
|
5
|
Reversal of Epigenetic Silencing Allows Robust HIV-1 Replication in the Absence of Integrase Function. mBio 2020; 11:mBio.01038-20. [PMID: 32487757 PMCID: PMC7267885 DOI: 10.1128/mbio.01038-20] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
While retroviral DNA is synthesized normally after infection by integrase-deficient viruses, the resultant episomal DNA is then epigenetically silenced. Here, we show that expression of the Tax transcription factor encoded by a second human retrovirus, HTLV-1, prevents or reverses the epigenetic silencing of unintegrated HIV-1 DNA and instead induces the addition of activating epigenetic marks and the recruitment of NF-κB/Rel proteins to the HIV-1 LTR promoter. Moreover, in the presence of Tax, the HIV-1 DNA circles that form in the absence of integrase function are not only efficiently transcribed but also support a spreading, pathogenic integrase-deficient (IN−) HIV-1 infection. Thus, retroviruses have the potential to replicate without integration, as is indeed seen with HBV. Moreover, these data suggest that integrase inhibitors may be less effective in the treatment of HIV-1 infections in individuals who are also coinfected with HTLV-1. Integration of the proviral DNA intermediate into the host cell genome normally represents an essential step in the retroviral life cycle. While the reason(s) for this requirement remains unclear, it is known that unintegrated proviral DNA is epigenetically silenced. Here, we demonstrate that human immunodeficiency virus 1 (HIV-1) mutants lacking a functional integrase (IN) can mount a robust, spreading infection in cells expressing the Tax transcription factor encoded by human T-cell leukemia virus 1 (HTLV-1). In these cells, HIV-1 forms episomal DNA circles, analogous to hepatitis B virus (HBV) covalently closed circular DNAs (cccDNAs), that are transcriptionally active and fully capable of supporting viral replication. In the presence of Tax, induced NF-κB proteins are recruited to the long terminal repeat (LTR) promoters present on unintegrated HIV-1 DNA, and this recruitment in turn correlates with the loss of inhibitory epigenetic marks and the acquisition of activating marks on histones bound to viral DNA. Therefore, HIV-1 is capable of replication in the absence of integrase function if the epigenetic silencing of unintegrated viral DNA can be prevented or reversed.
Collapse
|
6
|
Lampasona AA, Czaplinski K. Hnrnpab regulates neural cell motility through transcription of Eps8. RNA (NEW YORK, N.Y.) 2019; 25:45-59. [PMID: 30314980 PMCID: PMC6298563 DOI: 10.1261/rna.067413.118] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 10/01/2018] [Indexed: 05/05/2023]
Abstract
Cell migration requires a complicated network of structural and regulatory proteins. Changes in cellular motility can impact migration as a result of cell-type or developmental stage regulated expression of critical motility genes. Hnrnpab is a conserved RNA-binding protein found as two isoforms produced by alternative splicing. Its expression is enriched in the subventricular zone (SVZ) and the rostral migratory stream within the brain, suggesting possible support of the migration of neural progenitor cells in this region. Here we show that the migration of cells from the SVZ of developing Hnrnpab-/- mouse brains is impaired. An RNA-seq analysis to identify Hnrnpab-dependent cell motility genes led us to Eps8, and in agreement with the change in cell motility, we show that Eps8 is decreased in Hnrnpab-/- SVZ tissue. We scrutinized the motility of Hnrnpab-/- cells and confirmed that the decreases in both cell motility and Eps8 are restored by ectopically coexpressing both alternatively spliced Hnrnpab isoforms, therefore these variants are surprisingly nonredundant for cell motility. Our results support a model where both Hnrnpab isoforms work in concert to regulate Eps8 transcription in the mouse SVZ to promote the normal migration of neural cells during CNS development.
Collapse
Affiliation(s)
- Alexa A Lampasona
- Program in Molecular and Cellular Pharmacology, Stony Brook University, Stony Brook, New York 11749, USA
- Centers for Molecular Medicine, Stony Brook University, Stony Brook, New York 11749, USA
| | - Kevin Czaplinski
- Centers for Molecular Medicine, Stony Brook University, Stony Brook, New York 11749, USA
- Department of Anesthesiology, Stony Brook University, Stony Brook, New York 11749, USA
| |
Collapse
|
7
|
Poling BC, Price AM, Luftig MA, Cullen BR. The Epstein-Barr virus miR-BHRF1 microRNAs regulate viral gene expression in cis. Virology 2017; 512:113-123. [PMID: 28950226 DOI: 10.1016/j.virol.2017.09.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 09/05/2017] [Accepted: 09/18/2017] [Indexed: 10/18/2022]
Abstract
The Epstein-Barr virus (EBV) miR-BHRF1 microRNA (miRNA) cluster has been shown to facilitate B-cell transformation and promote the rapid growth of the resultant lymphoblastoid cell lines (LCLs). However, we find that expression of physiological levels of the miR-BHRF1 miRNAs in LCLs transformed with a miR-BHRF1 null mutant (∆123) fails to increase their growth rate. We demonstrate that the pri-miR-BHRF1-2 and 1-3 stem-loops are present in the 3'UTR of transcripts encoding EBNA-LP and that excision of pre-miR-BHRF1-2 and 1-3 by Drosha destabilizes these mRNAs and reduces expression of the encoded protein. Therefore, mutational inactivation of pri-miR-BHRF1-2 and 1-3 in the ∆123 mutant upregulates the expression of not only EBNA-LP but also EBNA-LP-regulated mRNAs and proteins, including LMP1. We hypothesize that this overexpression causes the reduced transformation capacity of the ∆123 EBV mutant. Thus, in addition to regulating cellular mRNAs in trans, miR-BHRF1-2 and 1-3 also regulate EBNA-LP mRNA expression in cis.
Collapse
Affiliation(s)
- Brigid Chiyoko Poling
- Department of Molecular Genetics & Microbiology and Center for Virology, Duke University Medical Center, Durham, NC, USA.
| | - Alexander M Price
- Department of Molecular Genetics & Microbiology and Center for Virology, Duke University Medical Center, Durham, NC, USA.
| | - Micah A Luftig
- Department of Molecular Genetics & Microbiology and Center for Virology, Duke University Medical Center, Durham, NC, USA.
| | - Bryan R Cullen
- Department of Molecular Genetics & Microbiology and Center for Virology, Duke University Medical Center, Durham, NC, USA.
| |
Collapse
|