1
|
Krishnan A, Ali LM, Prabhu SG, Pillai VN, Chameettachal A, Vivet-Boudou V, Bernacchi S, Mustafa F, Marquet R, Rizvi TA. Identification of a putative Gag binding site critical for feline immunodeficiency virus genomic RNA packaging. RNA (NEW YORK, N.Y.) 2023; 30:68-88. [PMID: 37914398 PMCID: PMC10726167 DOI: 10.1261/rna.079840.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 10/20/2023] [Indexed: 11/03/2023]
Abstract
The retroviral Gag precursor plays a central role in the selection and packaging of viral genomic RNA (gRNA) by binding to virus-specific packaging signal(s) (psi or ψ). Previously, we mapped the feline immunodeficiency virus (FIV) ψ to two discontinuous regions within the 5' end of the gRNA that assumes a higher order structure harboring several structural motifs. To better define the region and structural elements important for gRNA packaging, we methodically investigated these FIV ψ sequences using genetic, biochemical, and structure-function relationship approaches. Our mutational analysis revealed that the unpaired U85CUG88 stretch within FIV ψ is crucial for gRNA encapsidation into nascent virions. High-throughput selective 2' hydroxyl acylation analyzed by primer extension (hSHAPE) performed on wild type (WT) and mutant FIV ψ sequences, with substitutions in the U85CUG88 stretch, revealed that these mutations had limited structural impact and maintained nucleotides 80-92 unpaired, as in the WT structure. Since these mutations dramatically affected packaging, our data suggest that the single-stranded U85CUG88 sequence is important during FIV RNA packaging. Filter-binding assays performed using purified FIV Pr50Gag on WT and mutant U85CUG88 ψ RNAs led to reduced levels of Pr50Gag binding to mutant U85CUG88 ψ RNAs, indicating that the U85CUG88 stretch is crucial for ψ RNA-Pr50Gag interactions. Delineating sequences important for FIV gRNA encapsidation should enhance our understanding of both gRNA packaging and virion assembly, making them potential targets for novel retroviral therapeutic interventions, as well as the development of FIV-based vectors for human gene therapy.
Collapse
Affiliation(s)
- Anjana Krishnan
- Department of Microbiology and Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Lizna M Ali
- Department of Microbiology and Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Suresha G Prabhu
- Department of Microbiology and Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Vineeta N Pillai
- Department of Microbiology and Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Akhil Chameettachal
- Department of Microbiology and Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Valérie Vivet-Boudou
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR 9002, 67084 Strasbourg cedex, France
| | - Serena Bernacchi
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR 9002, 67084 Strasbourg cedex, France
| | - Farah Mustafa
- Department of Biochemistry, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
- Zayed bin Sultan Center for Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
- ASPIRE Research Institute in Precision Medicine, Abu Dhabi, United Arab Emirates
| | - Roland Marquet
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR 9002, 67084 Strasbourg cedex, France
| | - Tahir A Rizvi
- Department of Microbiology and Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
- Zayed bin Sultan Center for Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
- ASPIRE Research Institute in Precision Medicine, Abu Dhabi, United Arab Emirates
| |
Collapse
|
2
|
Chameettachal A, Mustafa F, Rizvi TA. Understanding Retroviral Life Cycle and its Genomic RNA Packaging. J Mol Biol 2023; 435:167924. [PMID: 36535429 DOI: 10.1016/j.jmb.2022.167924] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 12/12/2022] [Accepted: 12/12/2022] [Indexed: 12/23/2022]
Abstract
Members of the family Retroviridae are important animal and human pathogens. Being obligate parasites, their replication involves a series of steps during which the virus hijacks the cellular machinery. Additionally, many of the steps of retrovirus replication are unique among viruses, including reverse transcription, integration, and specific packaging of their genomic RNA (gRNA) as a dimer. Progress in retrovirology has helped identify several molecular mechanisms involved in each of these steps, but many are still unknown or remain controversial. This review summarizes our present understanding of the molecular mechanisms involved in various stages of retrovirus replication. Furthermore, it provides a comprehensive analysis of our current understanding of how different retroviruses package their gRNA into the assembling virions. RNA packaging in retroviruses holds a special interest because of the uniqueness of packaging a dimeric genome. Dimerization and packaging are highly regulated and interlinked events, critical for the virus to decide whether its unspliced RNA will be packaged as a "genome" or translated into proteins. Finally, some of the outstanding areas of exploration in the field of RNA packaging are highlighted, such as the role of epitranscriptomics, heterogeneity of transcript start sites, and the necessity of functional polyA sequences. An in-depth knowledge of mechanisms that interplay between viral and cellular factors during virus replication is critical in understanding not only the virus life cycle, but also its pathogenesis, and development of new antiretroviral compounds, vaccines, as well as retroviral-based vectors for human gene therapy.
Collapse
Affiliation(s)
- Akhil Chameettachal
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates. https://twitter.com/chameettachal
| | - Farah Mustafa
- Department of Biochemistry, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates; Zayed bin Sultan Center for Health Sciences (ZCHS), United Arab Emirates University, Al Ain, United Arab Emirates.
| | - Tahir A Rizvi
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates; Zayed bin Sultan Center for Health Sciences (ZCHS), United Arab Emirates University, Al Ain, United Arab Emirates.
| |
Collapse
|
3
|
Pillai VN, Ali LM, Prabhu SG, Krishnan A, Tariq S, Mustafa F, Rizvi TA. Expression, purification, and functional characterization of soluble recombinant full-length simian immunodeficiency virus (SIV) Pr55 Gag. Heliyon 2023; 9:e12892. [PMID: 36685375 PMCID: PMC9853374 DOI: 10.1016/j.heliyon.2023.e12892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 12/14/2022] [Accepted: 01/06/2023] [Indexed: 01/11/2023] Open
Abstract
The simian immunodeficiency virus (SIV) precursor polypeptide Pr55Gag drives viral assembly and facilitates specific recognition and packaging of the SIV genomic RNA (gRNA) into viral particles. While several studies have tried to elucidate the role of SIV Pr55Gag by expressing its different components independently, studies using full-length SIV Pr55Gag have not been conducted, primarily due to the unavailability of purified and biologically active full-length SIV Pr55Gag. We successfully expressed soluble, full-length SIV Pr55Gag with His6-tag in bacteria and purified it using affinity and gel filtration chromatography. In the process, we identified within Gag, a second in-frame start codon downstream of a putative Shine-Dalgarno-like sequence resulting in an additional truncated form of Gag. Synonymously mutating this sequence allowed expression of full-length Gag in its native form. The purified Gag assembled into virus-like particles (VLPs) in vitro in the presence of nucleic acids, revealing its biological functionality. In vivo experiments also confirmed formation of functional VLPs, and quantitative reverse transcriptase PCR demonstrated efficient packaging of SIV gRNA by these VLPs. The methodology we employed ensured the availability of >95% pure, biologically active, full-length SIV Pr55Gag which should facilitate future studies to understand protein structure and RNA-protein interactions involved during SIV gRNA packaging.
Collapse
Affiliation(s)
- Vineeta N. Pillai
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates
| | - Lizna Mohamed Ali
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates
| | - Suresha G. Prabhu
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates
| | - Anjana Krishnan
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates
| | - Saeed Tariq
- Department of Anatomy, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates
| | - Farah Mustafa
- Department of Biochemistry, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates,Zayed Center for Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates,Corresponding author. Department of Biochemistry, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), P.O. Box 15551, Al Ain, United Arab Emirates.
| | - Tahir A. Rizvi
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates,Zayed Center for Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates,Corresponding author. Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), P.O. Box 15551, Al Ain, United Arab Emirates.
| |
Collapse
|
4
|
Hochman J, Braitbard O. Life after Cleavage: The Story of a β-Retroviral (MMTV) Signal Peptide-From Murine Lymphoma to Human Breast Cancer. Viruses 2022; 14:v14112435. [PMID: 36366533 PMCID: PMC9694287 DOI: 10.3390/v14112435] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 10/31/2022] [Accepted: 10/31/2022] [Indexed: 11/06/2022] Open
Abstract
An increasing body of evidence in recent years supports an association of the betaretrovirus mouse mammary tumor virus (MMTV) with human breast cancer. This is an issue that still raises heated controversy. We have come to address this association using the signal peptide p14 of the MMTV envelope precursor protein as a key element of our strategy. In addition to its signal peptide function, p14 has some significant post endoplasmic reticulum (ER)-targeting characteristics: (1) it localizes to nucleoli where it binds key proteins (RPL5 and B23) involved (among other activities) in the regulation of nucleolar stress response, ribosome biogenesis and p53 stabilization; (2) p14 is a nuclear export factor; (3) it is expressed on the cell surface of infected cells, and as such, is amenable to, and successfully used, in preventive vaccination against experimental tumors that harbor MMTV; (4) the growth of such tumors is impaired in vivo using a combination of monoclonal anti-p14 antibodies or adoptive T-cell transfer treatments; (5) p14 is a phospho-protein endogenously phosphorylated by two different serine kinases. The phosphorylation status of the two sites determines whether p14 will function in an oncogenic or tumor-suppressing capacity; (6) transcriptional activation of genes (RPL5, ErbB4) correlates with the oncogenic potential of MMTV; (7) finally, polyclonal anti-p14 antibodies have been applied in immune histochemistry analyses of breast cancer cases using formalin fixed paraffin-embedded sections, supporting the associations of MMTV with the disease. Taken together, the above findings constitute a road map towards the diagnosis and possible prevention and treatment of MMTV-associated breast cancer.
Collapse
Affiliation(s)
- Jacob Hochman
- Department of Cell and Developmental Biology, Alexander Silberman Institute of Life Science, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
- Correspondence: ; Tel.: +972-54-441-4370
| | - Ori Braitbard
- Department of Cell and Developmental Biology, Alexander Silberman Institute of Life Science, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
- Department of Bioinformatics, The Faculty of Life and Health Sciences, Jerusalem College of Technology, Jerusalem 9372115, Israel
| |
Collapse
|
5
|
A Stretch of Unpaired Purines in the Leader Region of Simian Immunodeficiency Virus (SIV) Genomic RNA is Critical for its Packaging into Virions. J Mol Biol 2021; 433:167293. [PMID: 34624298 DOI: 10.1016/j.jmb.2021.167293] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 09/26/2021] [Accepted: 09/28/2021] [Indexed: 11/22/2022]
Abstract
Simian immunodeficiency virus (SIV) is an important lentivirus used as a non-human primate model to study HIV replication, and pathogenesis of human AIDS, as well as a potential vector for human gene therapy. This study investigated the role of single-stranded purines (ssPurines) as potential genomic RNA (gRNA) packaging determinants in SIV replication. Similar ssPurines have been implicated as important motifs for gRNA packaging in many retroviruses like, HIV-1, MPMV, and MMTV by serving as Gag binding sites during virion assembly. In examining the secondary structure of the SIV 5' leader region, as recently deduced using SHAPE methodology, we identified four specific stretches of ssPurines (I-IV) in the region that harbors major packaging determinants of SIV. The significance of these ssPurine motifs were investigated by mutational analysis coupled with a biologically relevant single round of replication assay. These analyses revealed that while ssPurine II was essential, the others (ssPurines I, III, & IV) did not significantly contribute to SIV gRNA packaging. Any mutation in the ssPurine II, such as its deletion or substitution, or other mutations that caused base pairing of ssPurine II loop resulted in near abrogation of RNA packaging, further substantiating the crucial role of ssPurine II and its looped conformation in SIV gRNA packaging. Structure prediction analysis of these mutants further corroborated the biological results and further revealed that the unpaired nature of ssPurine II is critical for its function during SIV RNA packaging perhaps by enabling it to function as a specific binding site for SIV Gag.
Collapse
|
6
|
Chameettachal A, Vivet-Boudou V, Pitchai F, Pillai V, Ali L, Krishnan A, Bernacchi S, Mustafa F, Marquet R, Rizvi T. A purine loop and the primer binding site are critical for the selective encapsidation of mouse mammary tumor virus genomic RNA by Pr77Gag. Nucleic Acids Res 2021; 49:4668-4688. [PMID: 33836091 PMCID: PMC8096270 DOI: 10.1093/nar/gkab223] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 03/15/2021] [Accepted: 03/24/2021] [Indexed: 12/22/2022] Open
Abstract
Retroviral RNA genome (gRNA) harbors cis-acting sequences that facilitate its specific packaging from a pool of other viral and cellular RNAs by binding with high-affinity to the viral Gag protein during virus assembly. However, the molecular intricacies involved during selective gRNA packaging are poorly understood. Binding and footprinting assays on mouse mammary tumor virus (MMTV) gRNA with purified Pr77Gag along with in cell gRNA packaging study identified two Pr77Gag binding sites constituting critical, non-redundant packaging signals. These included: a purine loop in a bifurcated stem-loop containing the gRNA dimerization initiation site, and the primer binding site (PBS). Despite these sites being present on both unspliced and spliced RNAs, Pr77Gag specifically bound to unspliced RNA, since only that could adopt the native bifurcated stem-loop structure containing looped purines. These results map minimum structural elements required to initiate MMTV gRNA packaging, distinguishing features that are conserved amongst divergent retroviruses from those perhaps unique to MMTV. Unlike purine-rich motifs frequently associated with packaging signals, direct involvement of PBS in gRNA packaging has not been documented in retroviruses. These results enhance our understanding of retroviral gRNA packaging/assembly, making it not only a target for novel therapeutic interventions, but also development of safer gene therapy vectors.
Collapse
Affiliation(s)
- Akhil Chameettachal
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Valérie Vivet-Boudou
- Université de Strasbourg, CNRS, Architecture et Réactivité de l’ARN, UPR 9002, Strasbourg, France
| | - Fathima Nuzra Nagoor Pitchai
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Vineeta N Pillai
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Lizna Mohamed Ali
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Anjana Krishnan
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Serena Bernacchi
- Université de Strasbourg, CNRS, Architecture et Réactivité de l’ARN, UPR 9002, Strasbourg, France
| | - Farah Mustafa
- Department of Biochemistry, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
- Zayed Center for Health Sciences, United Arab Emirates University, United Arab Emirates
| | - Roland Marquet
- Université de Strasbourg, CNRS, Architecture et Réactivité de l’ARN, UPR 9002, Strasbourg, France
| | - Tahir A Rizvi
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
- Zayed Center for Health Sciences, United Arab Emirates University, United Arab Emirates
| |
Collapse
|
7
|
Pitchai FNN, Chameettachal A, Vivet-Boudou V, Ali LM, Pillai VN, Krishnan A, Bernacchi S, Mustafa F, Marquet R, Rizvi TA. Identification of Pr78 Gag Binding Sites on the Mason-Pfizer Monkey Virus Genomic RNA Packaging Determinants. J Mol Biol 2021; 433:166923. [PMID: 33713677 DOI: 10.1016/j.jmb.2021.166923] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 03/01/2021] [Accepted: 03/01/2021] [Indexed: 02/04/2023]
Abstract
How retroviral Gag proteins recognize the packaging signals (Psi) on their genomic RNA (gRNA) is a key question that we addressed here using Mason-Pfizer monkey virus (MPMV) as a model system by combining band-shift assays and footprinting experiments. Our data show that Pr78Gag selects gRNA against spliced viral RNA by simultaneously binding to two single stranded loops on the MPMV Psi RNA: (1) a large purine loop (ssPurines), and (2) a loop which partially overlaps with a mostly base-paired purine repeat (bpPurines) and extends into a GU-rich binding motif. Importantly, this second Gag binding site is located immediately downstream of the major splice donor (mSD) and is thus absent from the spliced viral RNAs. Identifying elements crucial for MPMV gRNA packaging should help in understanding not only the mechanism of virion assembly by retroviruses, but also facilitate construction of safer retroviral vectors for human gene therapy.
Collapse
Affiliation(s)
- Fathima Nuzra Nagoor Pitchai
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Akhil Chameettachal
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Valérie Vivet-Boudou
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR 9002, Strasbourg, France
| | - Lizna Mohamed Ali
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Vineeta N Pillai
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Anjana Krishnan
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates
| | - Serena Bernacchi
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR 9002, Strasbourg, France
| | - Farah Mustafa
- Department of Biochemistry, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates; Zayed bin Sultan Center for Health Sciences, United Arab Emirates University, United Arab Emirates
| | - Roland Marquet
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR 9002, Strasbourg, France.
| | - Tahir A Rizvi
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), Al Ain, United Arab Emirates; Zayed bin Sultan Center for Health Sciences, United Arab Emirates University, United Arab Emirates.
| |
Collapse
|
8
|
Ali LM, Pitchai FNN, Vivet-Boudou V, Chameettachal A, Jabeen A, Pillai VN, Mustafa F, Marquet R, Rizvi TA. Role of Purine-Rich Regions in Mason-Pfizer Monkey Virus (MPMV) Genomic RNA Packaging and Propagation. Front Microbiol 2020; 11:595410. [PMID: 33250884 PMCID: PMC7674771 DOI: 10.3389/fmicb.2020.595410] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 09/25/2020] [Indexed: 12/13/2022] Open
Abstract
A distinguishing feature of the Mason-Pfizer monkey virus (MPMV) packaging signal RNA secondary structure is a single-stranded purine-rich sequence (ssPurines) in close vicinity to a palindromic stem loop (Pal SL) that functions as MPMV dimerization initiation site (DIS). However, unlike other retroviruses, MPMV contains a partially base-paired repeat sequence of ssPurines (bpPurines) in the adjacent region. Both purine-rich sequences have earlier been proposed to act as potentially redundant Gag binding sites to initiate the process of MPMV genomic RNA (gRNA) packaging. The objective of this study was to investigate the biological significance of ssPurines and bpPurines in MPMV gRNA packaging by systematic mutational and biochemical probing analyses. Deletion of either ssPurines or bpPurines individually had no significant effect on MPMV gRNA packaging, but it was severely compromised when both sequences were deleted simultaneously. Selective 2′ hydroxyl acylation analyzed by primer extension (SHAPE) analysis of the mutant RNAs revealed only mild effects on structure by deletion of either ssPurines or bpPurines, while the structure was dramatically affected by the two simultaneous deletions. This suggests that ssPurines and bpPurines play a redundant role in MPMV gRNA packaging, probably as Gag binding sites to facilitate gRNA capture and encapsidation. Interestingly, the deletion of bpPurines revealed an additional severe defect on RNA propagation that was independent of the presence or absence of ssPurines or the gRNA structure of the region. These findings further suggest that the bpPurines play an additional role in the early steps of MPMV replication cycle that is yet to be identified.
Collapse
Affiliation(s)
- Lizna Mohamed Ali
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Fathima Nuzra Nagoor Pitchai
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Valérie Vivet-Boudou
- Architecture et Réactivité de l'ARN, UPR 9002, IBMC, CNRS, Université de Strasbourg, Strasbourg, France
| | - Akhil Chameettachal
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Ayesha Jabeen
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Vineeta N Pillai
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Farah Mustafa
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates.,Zayed Center for Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Roland Marquet
- Architecture et Réactivité de l'ARN, UPR 9002, IBMC, CNRS, Université de Strasbourg, Strasbourg, France
| | - Tahir A Rizvi
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates.,Zayed Center for Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| |
Collapse
|
9
|
Rous Sarcoma Virus Genomic RNA Dimerization Capability In Vitro Is Not a Prerequisite for Viral Infectivity. Viruses 2020; 12:v12050568. [PMID: 32455905 PMCID: PMC7291142 DOI: 10.3390/v12050568] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 05/19/2020] [Accepted: 05/20/2020] [Indexed: 12/29/2022] Open
Abstract
Retroviruses package their full-length, dimeric genomic RNA (gRNA) via specific interactions between the Gag polyprotein and a “Ψ” packaging signal located in the gRNA 5′-UTR. Rous sarcoma virus (RSV) gRNA has a contiguous, well-defined Ψ element, that directs the packaging of heterologous RNAs efficiently. The simplicity of RSV Ψ makes it an informative model to examine the mechanism of retroviral gRNA packaging, which is incompletely understood. Little is known about the structure of dimerization initiation sites or specific Gag interaction sites of RSV gRNA. Using selective 2′-hydroxyl acylation analyzed by primer extension (SHAPE), we probed the secondary structure of the entire RSV 5′-leader RNA for the first time. We identified a putative bipartite dimerization initiation signal (DIS), and mutation of both sites was required to significantly reduce dimerization in vitro. These mutations failed to reduce viral replication, suggesting that in vitro dimerization results do not strictly correlate with in vivo infectivity, possibly due to additional RNA interactions that maintain the dimers in cells. UV crosslinking-coupled SHAPE (XL-SHAPE) was next used to determine Gag-induced RNA conformational changes, revealing G218 as a critical Gag contact site. Overall, our results suggest that disruption of either of the DIS sequences does not reduce virus replication and reveal specific sites of Gag–RNA interactions.
Collapse
|
10
|
Gumna J, Purzycka KJ, Ahn HW, Garfinkel DJ, Pachulska-Wieczorek K. Retroviral-like determinants and functions required for dimerization of Ty1 retrotransposon RNA. RNA Biol 2019; 16:1749-1763. [PMID: 31469343 PMCID: PMC6844567 DOI: 10.1080/15476286.2019.1657370] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
During replication of long terminal repeat (LTR)-retrotransposons, their proteins and genome (g) RNA assemble into virus-like particles (VLPs) that are not infectious but functionally related to retroviral virions. Both virions and VLPs contain gRNA in a dimeric form, but contrary to retroviruses, little is known about how gRNA dimerization and packaging occurs in LTR-retrotransposons. The LTR-retrotransposon Ty1 from Saccharomyces cerevisiae is an informative model for studying LTR-retrotransposon and retrovirus replication. Using structural, mutational and functional analyses, we explored dimerization of Ty1 genomic RNA. We provide direct evidence that interactions of self-complementary PAL1 and PAL2 palindromic sequences localized within the 5′UTR are essential for Ty1 gRNA dimer formation. Mutations disrupting PAL1-PAL2 complementarity restricted RNA dimerization in vitro and Ty1 mobility in vivo. Although dimer formation and mobility of these mutants was inhibited, our work suggests that Ty1 RNA can dimerize via alternative contact points. In contrast to previous studies, we cannot confirm a role for PAL3, tRNAiMet as well as recently proposed initial kissing-loop interactions in dimer formation. Our data also supports the critical role of Ty1 Gag in RNA dimerization. Mature Ty1 Gag binds in the proximity of sequences involved in RNA dimerization and tRNAiMet annealing, but the 5′ pseudoknot in Ty1 RNA may constitute a preferred Gag-binding site. Taken together, these results expand our understanding of genome dimerization and packaging strategies utilized by LTR-retroelements.
Collapse
Affiliation(s)
- Julita Gumna
- Department of Structure and Function of Retrotransposons, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Katarzyna J Purzycka
- Department of Structure and Function of Retrotransposons, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Hyo Won Ahn
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - David J Garfinkel
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Katarzyna Pachulska-Wieczorek
- Department of Structure and Function of Retrotransposons, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| |
Collapse
|
11
|
Kalloush RM, Vivet-Boudou V, Ali LM, Pillai VN, Mustafa F, Marquet R, Rizvi TA. Stabilizing role of structural elements within the 5´ Untranslated Region (UTR) and gag sequences in Mason-Pfizer monkey virus (MPMV) genomic RNA packaging. RNA Biol 2019; 16:612-625. [PMID: 30773097 DOI: 10.1080/15476286.2019.1572424] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
The Mason-Pfizer monkey virus (MPMV) genomic RNA (gRNA) packaging signal is a highly-structured element with several stem-loops held together by two phylogenetically conserved long-range interactions (LRIs) between U5 and gag complementary sequences. These LRIs play a critical role in maintaining the structure of the 5´ end of the MPMV gRNA. Thus, one could hypothesize that the overall RNA secondary structure of this region is further architecturally held together by three other stem loops (SL3, Gag SL1, and Gag SL2) comprising of sequences from the distal parts of the 5´untranslated region (5' UTR) to ~ 120 nucleotides into gag, excluding gag sequences involved in forming the U5-Gag LRIs. To provide functional evidence for the biological significance of these stem loops during gRNA encapsidation, these structural motifs were mutated and their effects on MPMV RNA packaging and propagation were tested in a single round trans-complementation assay. The mutant RNA structures were further studied by high throughput SHAPE (hSHAPE) assay. Our results reveal that sequences involved in forming these three stem loops do not play crucial roles at an individual level during MPMV gRNA packaging or propagation. Further structure-function analysis indicates that the U5-Gag LRIs have a more important architectural role in stabilizing the higher order structure of the 5´ UTR than the three stem loops which have a more secondary and perhaps indirect role in stabilizing the overall RNA secondary structure of the region. Our work provides a better understanding of the molecular interactions that take place during MPMV gRNA packaging.
Collapse
Affiliation(s)
- Rawan M Kalloush
- a Department of Microbiology & Immunology College of Medicine and Health Sciences , United Arab Emirates University , Al Ain , United Arab Emirates (UAE)
| | - Valérie Vivet-Boudou
- b CNRS, Architecture et Réactivité de l'ARN, UPR , Université de Strasbourg , Strasbourg , France
| | - Lizna M Ali
- a Department of Microbiology & Immunology College of Medicine and Health Sciences , United Arab Emirates University , Al Ain , United Arab Emirates (UAE)
| | - Vineeta N Pillai
- a Department of Microbiology & Immunology College of Medicine and Health Sciences , United Arab Emirates University , Al Ain , United Arab Emirates (UAE)
| | - Farah Mustafa
- c Department of Biochemistry, College of Medicine and Health Sciences , United Arab Emirates University , Al Ain , United Arab Emirates (UAE)
| | - Roland Marquet
- b CNRS, Architecture et Réactivité de l'ARN, UPR , Université de Strasbourg , Strasbourg , France
| | - Tahir A Rizvi
- a Department of Microbiology & Immunology College of Medicine and Health Sciences , United Arab Emirates University , Al Ain , United Arab Emirates (UAE)
| |
Collapse
|
12
|
Akhlaq S, Panicker NG, Philip PS, Ali LM, Dudley JP, Rizvi TA, Mustafa F. A cis-Acting Element Downstream of the Mouse Mammary Tumor Virus Major Splice Donor Critical for RNA Elongation and Stability. J Mol Biol 2018; 430:4307-4324. [PMID: 30179605 DOI: 10.1016/j.jmb.2018.08.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Revised: 08/28/2018] [Accepted: 08/28/2018] [Indexed: 12/11/2022]
Abstract
BACKGROUND The mouse mammary tumor virus (MMTV) encodes a functional signal peptide, a cleavage product of envelope and Rem proteins. Signal peptide interacts with a 3' cis-acting RNA element, the Rem-responsive element (RmRE), to facilitate expression of both unspliced genomic (gRNA) and spliced mRNAs. An additional RmRE has been proposed at the 5' end of the genome, facilitating nuclear export of the unspliced gRNA, whereas the 3' RmRE could facilitate translation of all other mRNAs, including gRNA. RESULTS To address this hypothesis, a series of mutations were introduced into a 24-nt region found exclusively in the unspliced gRNA. Mutant clones using MMTV or human cytomegalovirus promoters were tested in both transient and stable transfections to determine their effect on gRNA nuclear export, stability, and translation. Nuclear export of the gRNA was affected only in a small mutant subset in stably transfected Jurkat T cells. Quantitative real-time RT-PCR of actinomycin D-treated cells expressing MMTV revealed that multiple mutants were severely compromised for RNA expression and stability. Both genomic and spliced nuclear RNAs were reduced, leading to abrogation of Gag and Env protein expressed from unspliced and spliced mRNAs, respectively. RT-PCRs with multiple primer pairs indicated failure to elongate genomic MMTV transcripts beyond ~500 nt compared to the wild type in a cell line-dependent manner. CONCLUSIONS MMTV contains a novel cis-acting element downstream of the major splice donor critical for facilitating MMTV gRNA elongation and stability. Presence of a mirror repeat within the element may represent important viral/host factor binding site(s) within MMTV gRNA.
Collapse
Affiliation(s)
- Shaima Akhlaq
- Department of Biochemistry, College of Medicine and Health Sciences, UAE University, Tawam Hospital Complex, P.O. Box 17666, Al Ain, United Arab Emirates.
| | - Neena G Panicker
- Department of Biochemistry, College of Medicine and Health Sciences, UAE University, Tawam Hospital Complex, P.O. Box 17666, Al Ain, United Arab Emirates.
| | - Pretty S Philip
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, UAE University, Tawam Hospital Complex, P.O. Box 17666, Al Ain, United Arab Emirates.
| | - Lizna M Ali
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, UAE University, Tawam Hospital Complex, P.O. Box 17666, Al Ain, United Arab Emirates.
| | - Jaquelin P Dudley
- LaMontagne Center for Infectious Diseases, The University of Texas at Austin, 100 East 24th Street, NHB 2.616, Austin, TX 78712, USA.
| | - Tahir A Rizvi
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, UAE University, Tawam Hospital Complex, P.O. Box 17666, Al Ain, United Arab Emirates.
| | - Farah Mustafa
- Department of Biochemistry, College of Medicine and Health Sciences, UAE University, Tawam Hospital Complex, P.O. Box 17666, Al Ain, United Arab Emirates.
| |
Collapse
|
13
|
Pitchai FNN, Ali L, Pillai VN, Chameettachal A, Ashraf SS, Mustafa F, Marquet R, Rizvi TA. Expression, purification, and characterization of biologically active full-length Mason-Pfizer monkey virus (MPMV) Pr78 Gag. Sci Rep 2018; 8:11793. [PMID: 30087395 PMCID: PMC6081465 DOI: 10.1038/s41598-018-30142-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 07/20/2018] [Indexed: 02/07/2023] Open
Abstract
MPMV precursor polypeptide Pr78Gag orchestrates assembly and packaging of genomic RNA (gRNA) into virus particles. Therefore, we have expressed recombinant full-length Pr78Gag either with or without His6-tag in bacterial as well as eukaryotic cultures and purified the recombinant protein from soluble fractions of the bacterial cultures. The recombinant Pr78Gag protein has the intrinsic ability to assemble in vitro to form virus like particles (VLPs). Consistent with this observation, the recombinant protein could form VLPs in both prokaryotes and eukaryotes. VLPs formed in eukaryotic cells by recombinant Pr78Gag with or without His6-tag can encapsidate MPMV transfer vector RNA, suggesting that the inclusion of the His6-tag to the full-length Pr78Gag did not interfere with its expression or biological function. This study demonstrates the expression and purification of a biologically active, recombinant Pr78Gag, which should pave the way to study RNA-protein interactions involved in the MPMV gRNA packaging process.
Collapse
Affiliation(s)
- Fathima Nuzra Nagoor Pitchai
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Lizna Ali
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Vineeta Narayana Pillai
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Akhil Chameettachal
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Syed Salman Ashraf
- Department of Chemistry, College of Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Farah Mustafa
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Roland Marquet
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR, 9002, Strasbourg, France.
| | - Tahir Aziz Rizvi
- Department of Microbiology & Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates.
| |
Collapse
|
14
|
Mustafa F, Vivet-Boudou V, Jabeen A, Ali LM, Kalloush RM, Marquet R, Rizvi TA. The bifurcated stem loop 4 (SL4) is crucial for efficient packaging of mouse mammary tumor virus (MMTV) genomic RNA. RNA Biol 2018; 15:1047-1059. [PMID: 29929424 PMCID: PMC6161677 DOI: 10.1080/15476286.2018.1486661] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Packaging the mouse mammary tumor virus (MMTV) genomic RNA (gRNA) requires the entire 5' untranslated region (UTR) in conjunction with the first 120 nucleotides of the gag gene. This region includes several palindromic (pal) sequence(s) and stable stem loops (SLs). Among these, stem loop 4 (SL4) adopts a bifurcated structure consisting of three stems, two apical loops, and an internal loop. Pal II, located in one of the apical loops, mediates gRNA dimerization, a process intricately linked to packaging. We thus hypothesized that the bifurcated SL4 structure could constitute the major gRNA packaging determinant. To test this hypothesis, the two apical loops and the flanking sequences forming the bifurcated SL4 were individually mutated. These mutations all had deleterious effects on gRNA packaging and propagation. Next, single and compensatory mutants were designed to destabilize then recreate the bifurcated SL4 structure. A structure-function analysis using bioinformatics predictions and RNA chemical probing revealed that mutations that led to the loss of the SL4 bifurcated structure abrogated RNA packaging and propagation, while compensatory mutations that recreated the native SL4 structure restored RNA packaging and propagation to wild type levels. Altogether, our results demonstrate that SL4 constitutes the principal packaging determinant of MMTV gRNA. Our findings further suggest that SL4 acts as a structural switch that can not only differentiate between RNA for translation versus packaging/dimerization, but its location also allows differentiation between spliced and unspliced RNAs during gRNA encapsidation.
Collapse
Affiliation(s)
- Farah Mustafa
- a Department of Biochemistry , College of Medicine and Health Sciences, United Arab Emirates University , Al Ain , UAE
| | - Valérie Vivet-Boudou
- b Université de Strasbourg , CNRS, Architecture et Réactivité de l'ARN , Strasbourg , France
| | - Ayesha Jabeen
- c Department of Microbiology & Immunology , College of Medicine and Health Sciences, United Arab Emirates University , Al Ain , UAE
| | - Lizna M Ali
- c Department of Microbiology & Immunology , College of Medicine and Health Sciences, United Arab Emirates University , Al Ain , UAE
| | - Rawan M Kalloush
- c Department of Microbiology & Immunology , College of Medicine and Health Sciences, United Arab Emirates University , Al Ain , UAE
| | - Roland Marquet
- b Université de Strasbourg , CNRS, Architecture et Réactivité de l'ARN , Strasbourg , France
| | - Tahir A Rizvi
- c Department of Microbiology & Immunology , College of Medicine and Health Sciences, United Arab Emirates University , Al Ain , UAE
| |
Collapse
|
15
|
Biochemical and Functional Characterization of Mouse Mammary Tumor Virus Full-Length Pr77 Gag Expressed in Prokaryotic and Eukaryotic Cells. Viruses 2018; 10:v10060334. [PMID: 29912170 PMCID: PMC6024702 DOI: 10.3390/v10060334] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 06/11/2018] [Accepted: 06/14/2018] [Indexed: 12/15/2022] Open
Abstract
The mouse mammary tumor virus (MMTV) Pr77Gag polypeptide is an essential retroviral structural protein without which infectious viral particles cannot be formed. This process requires specific recognition and packaging of dimerized genomic RNA (gRNA) by Gag during virus assembly. Most of the previous work on retroviral assembly has used either the nucleocapsid portion of Gag, or other truncated Gag derivatives—not the natural substrate for virus assembly. In order to understand the molecular mechanism of MMTV gRNA packaging process, we expressed and purified full-length recombinant Pr77Gag-His6-tag fusion protein from soluble fractions of bacterial cultures. We show that the purified Pr77Gag-His6-tag protein retained the ability to assemble virus-like particles (VLPs) in vitro with morphologically similar immature intracellular particles. The recombinant proteins (with and without His6-tag) could both be expressed in prokaryotic and eukaryotic cells and had the ability to form VLPs in vivo. Most importantly, the recombinant Pr77Gag-His6-tag fusion proteins capable of making VLPs in eukaryotic cells were competent for packaging sub-genomic MMTV RNAs. The successful expression and purification of a biologically active, full-length MMTV Pr77Gag should lay down the foundation towards performing RNA–protein interaction(s), especially for structure-function studies and towards understanding molecular intricacies during MMTV gRNA packaging and assembly processes.
Collapse
|
16
|
Mutations in the Basic Region of the Mason-Pfizer Monkey Virus Nucleocapsid Protein Affect Reverse Transcription, Genomic RNA Packaging, and the Virus Assembly Site. J Virol 2018; 92:JVI.00106-18. [PMID: 29491167 DOI: 10.1128/jvi.00106-18] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 02/20/2018] [Indexed: 12/19/2022] Open
Abstract
In addition to specific RNA-binding zinc finger domains, the retroviral Gag polyprotein contains clusters of basic amino acid residues that are thought to support Gag-viral genomic RNA (gRNA) interactions. One of these clusters is the basic K16NK18EK20 region, located upstream of the first zinc finger of the Mason-Pfizer monkey virus (M-PMV) nucleocapsid (NC) protein. To investigate the role of this basic region in the M-PMV life cycle, we used a combination of in vivo and in vitro methods to study a series of mutants in which the overall charge of this region was more positive (RNRER), more negative (AEAEA), or neutral (AAAAA). The mutations markedly affected gRNA incorporation and the onset of reverse transcription. The introduction of a more negative charge (AEAEA) significantly reduced the incorporation of M-PMV gRNA into nascent particles. Moreover, the assembly of immature particles of the AEAEA Gag mutant was relocated from the perinuclear region to the plasma membrane. In contrast, an enhancement of the basicity of this region of M-PMV NC (RNRER) caused a substantially more efficient incorporation of gRNA, subsequently resulting in an increase in M-PMV RNRER infectivity. Nevertheless, despite the larger amount of gRNA packaged by the RNRER mutant, the onset of reverse transcription was delayed in comparison to that of the wild type. Our data clearly show the requirement for certain positively charged amino acid residues upstream of the first zinc finger for proper gRNA incorporation, assembly of immature particles, and proceeding of reverse transcription.IMPORTANCE We identified a short sequence within the Gag polyprotein that, together with the zinc finger domains and the previously identified RKK motif, contributes to the packaging of genomic RNA (gRNA) of Mason-Pfizer monkey virus (M-PMV). Importantly, in addition to gRNA incorporation, this basic region (KNKEK) at the N terminus of the nucleocapsid protein is crucial for the onset of reverse transcription. Mutations that change the positive charge of the region to a negative one significantly reduced specific gRNA packaging. The assembly of immature particles of this mutant was reoriented from the perinuclear region to the plasma membrane. On the contrary, an enhancement of the basic character of this region increased both the efficiency of gRNA packaging and the infectivity of the virus. However, the onset of reverse transcription was delayed even in this mutant. In summary, the basic region in M-PMV Gag plays a key role in the packaging of genomic RNA and, consequently, in assembly and reverse transcription.
Collapse
|
17
|
Wojciechowska M, Dudek M, Trylska J. Thermodynamics of the pseudo-knot in helix 18 of 16S ribosomal RNA. Biopolymers 2018; 109:e23116. [PMID: 29570767 DOI: 10.1002/bip.23116] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 02/24/2018] [Accepted: 02/27/2018] [Indexed: 01/13/2023]
Abstract
A fragment of E. coli 16S rRNA formed by nucleotides 500 to 545 is termed helix 18. Nucleotides 505-507 and 524-526 form a pseudo-knot and its distortion affects ribosome function. Helix 18 isolated from the ribosome context is thus an interesting fragment to investigate the structural properties and folding of RNA with pseudo-knots. With all-atom molecular dynamics simulations, spectroscopic and gel electrophoresis experiments, we investigated thermodynamics of helix 18, with a focus on its pseudo-knot. In solution studies at ambient conditions we observed dimerization of helix 18. We proposed that the loop, containing nucleotides forming the pseudo-knot, interacts with another monomer of helix 18. The native dimer is difficult to break but introducing mutations in the pseudo-knot indeed assured a monomeric form of helix 18. Molecular dynamics simulations at 310 K confirmed the stability of the pseudo-knot but at elevated temperatures this pseudo-knot was the first part of helix 18 to lose the hydrogen bond pattern. To further determine helix 18 stability, we analyzed the interactions of helix 18 with short oligomers complementary to a nucleotide stretch containing the pseudo-knot. The formation of higher-order structures by helix 18 impacts hybridization efficiency of peptide nucleic acid and 2'-O methyl RNA oligomers.
Collapse
Affiliation(s)
- Monika Wojciechowska
- Centre of New Technologies, University of Warsaw, Banacha 2C, Warsaw, 02-09, Poland
| | - Marta Dudek
- Centre of New Technologies, University of Warsaw, Banacha 2C, Warsaw, 02-09, Poland.,School of Molecular Biology, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, Warsaw, 02-106, Poland.,First Faculty of Medicine, Department of Hematology, Oncology and Internal Diseases, Medical University of Warsaw, Al. Żwirki i Wigury 61, Warsaw, 02-091, Poland
| | - Joanna Trylska
- Centre of New Technologies, University of Warsaw, Banacha 2C, Warsaw, 02-09, Poland
| |
Collapse
|
18
|
Dubois N, Marquet R, Paillart JC, Bernacchi S. Retroviral RNA Dimerization: From Structure to Functions. Front Microbiol 2018; 9:527. [PMID: 29623074 PMCID: PMC5874298 DOI: 10.3389/fmicb.2018.00527] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 03/08/2018] [Indexed: 01/18/2023] Open
Abstract
The genome of the retroviruses is a dimer composed by two homologous copies of genomic RNA (gRNA) molecules of positive polarity. The dimerization process allows two gRNA molecules to be non-covalently linked together through intermolecular base-pairing. This step is critical for the viral life cycle and is highly conserved among retroviruses with the exception of spumaretroviruses. Furthermore, packaging of two gRNA copies into viral particles presents an important evolutionary advantage for immune system evasion and drug resistance. Recent studies reported RNA switches models regulating not only gRNA dimerization, but also translation and packaging, and a spatio-temporal characterization of viral gRNA dimerization within cells are now at hand. This review summarizes our current understanding on the structural features of the dimerization signals for a variety of retroviruses (HIVs, MLV, RSV, BLV, MMTV, MPMV…), the mechanisms of RNA dimer formation and functional implications in the retroviral cycle.
Collapse
Affiliation(s)
- Noé Dubois
- Architecture et Réactivité de l'ARN, UPR 9002, IBMC, CNRS, Université de Strasbourg, Strasbourg, France
| | - Roland Marquet
- Architecture et Réactivité de l'ARN, UPR 9002, IBMC, CNRS, Université de Strasbourg, Strasbourg, France
| | - Jean-Christophe Paillart
- Architecture et Réactivité de l'ARN, UPR 9002, IBMC, CNRS, Université de Strasbourg, Strasbourg, France
| | - Serena Bernacchi
- Architecture et Réactivité de l'ARN, UPR 9002, IBMC, CNRS, Université de Strasbourg, Strasbourg, France
| |
Collapse
|
19
|
Jayaraman D, Kenyon JC. New windows into retroviral RNA structures. Retrovirology 2018; 15:11. [PMID: 29368653 PMCID: PMC5784592 DOI: 10.1186/s12977-018-0393-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 01/12/2018] [Indexed: 12/16/2022] Open
Abstract
Background The multiple roles of both viral and cellular RNAs have become increasingly apparent in recent years, and techniques to model them have become significantly more powerful, enabling faster and more accurate visualization of RNA structures. Main body Techniques such as SHAPE (selective 2’OH acylation analysed by primer extension) have revolutionized the field, and have been used to examine RNAs belonging to many and diverse retroviruses. Secondary structure probing reagents such as these have been aided by the development of faster methods of analysis either via capillary or next-generation sequencing, allowing the analysis of entire genomes, and of retroviral RNA structures within virions. Techniques to model the three-dimensional structures of these large RNAs have also recently developed. Conclusions The flexibility of retroviral RNAs, both structural and functional, is clear from the results of these new experimental techniques. Retroviral RNA structures and structural changes control many stages of the lifecycle, and both the RNA structures themselves and their interactions with ligands are potential new drug targets. In addition, our growing understanding of retroviral RNA structures is aiding our knowledge of cellular RNA form and function.
Collapse
Affiliation(s)
- Dhivya Jayaraman
- Department of Medicine, National University of Singapore, 14 Medical Drive, MD 6, Level 15, Singapore, 117599, Singapore
| | - Julia Claire Kenyon
- Department of Medicine, University of Cambridge, Level 5 Addenbrookes Hospital Hills Rd, Cambridge, CB2 0QQ, UK. .,Department of Microbiology and Immunology, National University of Singapore, 5 Science Drive 2 Blk MD4, Level 3, Singapore, 117545, Singapore. .,Homerton College, University of Cambridge, Hills Rd, Cambridge, CB2 8PH, UK.
| |
Collapse
|
20
|
Diaz-Toledano R, Lozano G, Martinez-Salas E. In-cell SHAPE uncovers dynamic interactions between the untranslated regions of the foot-and-mouth disease virus RNA. Nucleic Acids Res 2017; 45:1416-1432. [PMID: 28180318 PMCID: PMC5388415 DOI: 10.1093/nar/gkw795] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 08/26/2016] [Accepted: 08/29/2016] [Indexed: 12/14/2022] Open
Abstract
The genome of RNA viruses folds into 3D structures that include long-range RNA–RNA interactions relevant to control critical steps of the viral cycle. In particular, initiation of translation driven by the IRES element of foot-and-mouth disease virus is stimulated by the 3΄UTR. Here we sought to investigate the RNA local flexibility of the IRES element and the 3΄UTR in living cells. The SHAPE reactivity observed in vivo showed statistically significant differences compared to the free RNA, revealing protected or exposed positions within the IRES and the 3΄UTR. Importantly, the IRES local flexibility was modified in the presence of the 3΄UTR, showing significant protections at residues upstream from the functional start codon. Conversely, presence of the IRES element in cis altered the 3΄UTR local flexibility leading to an overall enhanced reactivity. Unlike the reactivity changes observed in the IRES element, the SHAPE differences of the 3΄UTR were large but not statistically significant, suggesting multiple dynamic RNA interactions. These results were supported by covariation analysis, which predicted IRES-3΄UTR conserved helices in agreement with the protections observed by SHAPE probing. Mutational analysis suggested that disruption of one of these interactions could be compensated by alternative base pairings, providing direct evidences for dynamic long-range interactions between these distant elements of the viral genome.
Collapse
Affiliation(s)
- Rosa Diaz-Toledano
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid, Nicolas Cabrera 1, Madrid, Spain
| | - Gloria Lozano
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid, Nicolas Cabrera 1, Madrid, Spain
| | - Encarnacion Martinez-Salas
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid, Nicolas Cabrera 1, Madrid, Spain
| |
Collapse
|
21
|
Bernacchi S, Abd El-Wahab EW, Dubois N, Hijnen M, Smyth RP, Mak J, Marquet R, Paillart JC. HIV-1 Pr55 Gag binds genomic and spliced RNAs with different affinity and stoichiometry. RNA Biol 2016; 14:90-103. [PMID: 27841704 DOI: 10.1080/15476286.2016.1256533] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
The HIV-1 Pr55Gag precursor specifically selects genomic RNA (gRNA) from a large variety of cellular and spliced viral RNAs (svRNAs), however the molecular mechanisms of this selective recognition remains poorly understood. To gain better understanding of this process, we analyzed the interactions between Pr55Gag and a large panel of viral RNA (vRNA) fragments encompassing the main packaging signal (Psi) and its flanking regions by fluorescence spectroscopy. We showed that the gRNA harbors a high affinity binding site which is absent from svRNA species, suggesting that this site might be crucial for selecting the HIV-1 genome. Our stoichiometry analysis of protein/RNA complexes revealed that few copies of Pr55Gag specifically associate with the 5' region of the gRNA. Besides, we found that gRNA dimerization significantly impacts Pr55Gag binding, and we confirmed that the internal loop of stem-loop 1 (SL1) in Psi is crucial for specific interaction with Pr55Gag. Our analysis of gRNA fragments of different length supports the existence of a long-range tertiary interaction involving sequences upstream and downstream of the Psi region. This long-range interaction might promote optimal exposure of SL1 for efficient Pr55Gag recognition. Altogether, our results shed light on the molecular mechanisms allowing the specific selection of gRNA by Pr55Gag among a variety of svRNAs, all harboring SL1 in their first common exon.
Collapse
Affiliation(s)
- Serena Bernacchi
- a Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN , Strasbourg , France
| | - Ekram W Abd El-Wahab
- a Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN , Strasbourg , France
| | - Noé Dubois
- a Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN , Strasbourg , France
| | - Marcel Hijnen
- b Centre for Virology, Burnet Institute , Melbourne , Victoria , Australia.,c Department of Biochemistry and Molecular Biology , Monash University , Clayton , Victoria , Australia
| | - Redmond P Smyth
- a Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN , Strasbourg , France
| | - Johnson Mak
- b Centre for Virology, Burnet Institute , Melbourne , Victoria , Australia.,c Department of Biochemistry and Molecular Biology , Monash University , Clayton , Victoria , Australia.,d School of Medicine, Faculty of Health, Deakin University , Geelong , Victoria , Australia.,e Commonwealth Scientific and Industrial Research Organization, Livestock Industries, Australian Animal Health Laboratory , Geelong , Victoria , Australia
| | - Roland Marquet
- a Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN , Strasbourg , France
| | | |
Collapse
|
22
|
Cross- and Co-Packaging of Retroviral RNAs and Their Consequences. Viruses 2016; 8:v8100276. [PMID: 27727192 PMCID: PMC5086612 DOI: 10.3390/v8100276] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 10/03/2016] [Accepted: 10/03/2016] [Indexed: 12/23/2022] Open
Abstract
Retroviruses belong to the family Retroviridae and are ribonucleoprotein (RNP) particles that contain a dimeric RNA genome. Retroviral particle assembly is a complex process, and how the virus is able to recognize and specifically capture the genomic RNA (gRNA) among millions of other cellular and spliced retroviral RNAs has been the subject of extensive investigation over the last two decades. The specificity towards RNA packaging requires higher order interactions of the retroviral gRNA with the structural Gag proteins. Moreover, several retroviruses have been shown to have the ability to cross-/co-package gRNA from other retroviruses, despite little sequence homology. This review will compare the determinants of gRNA encapsidation among different retroviruses, followed by an examination of our current understanding of the interaction between diverse viral genomes and heterologous proteins, leading to their cross-/co-packaging. Retroviruses are well-known serious animal and human pathogens, and such a cross-/co-packaging phenomenon could result in the generation of novel viral variants with unknown pathogenic potential. At the same time, however, an enhanced understanding of the molecular mechanisms involved in these specific interactions makes retroviruses an attractive target for anti-viral drugs, vaccines, and vectors for human gene therapy.
Collapse
|
23
|
Orchestrating the Selection and Packaging of Genomic RNA by Retroviruses: An Ensemble of Viral and Host Factors. Viruses 2016; 8:v8090257. [PMID: 27657110 PMCID: PMC5035971 DOI: 10.3390/v8090257] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Revised: 09/09/2016] [Accepted: 09/13/2016] [Indexed: 12/31/2022] Open
Abstract
Infectious retrovirus particles contain two copies of unspliced viral RNA that serve as the viral genome. Unspliced retroviral RNA is transcribed in the nucleus by the host RNA polymerase II and has three potential fates: (1) it can be spliced into subgenomic messenger RNAs (mRNAs) for the translation of viral proteins; or it can remain unspliced to serve as either (2) the mRNA for the translation of Gag and Gag-Pol; or (3) the genomic RNA (gRNA) that is packaged into virions. The Gag structural protein recognizes and binds the unspliced viral RNA to select it as a genome, which is selected in preference to spliced viral RNAs and cellular RNAs. In this review, we summarize the current state of understanding about how retroviral packaging is orchestrated within the cell and explore potential new mechanisms based on recent discoveries in the field. We discuss the cis-acting elements in the unspliced viral RNA and the properties of the Gag protein that are required for their interaction. In addition, we discuss the role of host factors in influencing the fate of the newly transcribed viral RNA, current models for how retroviruses distinguish unspliced viral mRNA from viral genomic RNA, and the possible subcellular sites of genomic RNA dimerization and selection by Gag. Although this review centers primarily on the wealth of data available for the alpharetrovirus Rous sarcoma virus, in which a discrete RNA packaging sequence has been identified, we have also summarized the cis- and trans-acting factors as well as the mechanisms governing gRNA packaging of other retroviruses for comparison.
Collapse
|
24
|
The Life-Cycle of the HIV-1 Gag-RNA Complex. Viruses 2016; 8:v8090248. [PMID: 27626439 PMCID: PMC5035962 DOI: 10.3390/v8090248] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 08/30/2016] [Accepted: 09/02/2016] [Indexed: 12/16/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) replication is a highly regulated process requiring the recruitment of viral and cellular components to the plasma membrane for assembly into infectious particles. This review highlights the recent process of understanding the selection of the genomic RNA (gRNA) by the viral Pr55Gag precursor polyprotein, and the processes leading to its incorporation into viral particles.
Collapse
|
25
|
Ferrer M, Henriet S, Chamontin C, Lainé S, Mougel M. From Cells to Virus Particles: Quantitative Methods to Monitor RNA Packaging. Viruses 2016; 8:v8080239. [PMID: 27556480 PMCID: PMC4997601 DOI: 10.3390/v8080239] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 08/16/2016] [Accepted: 08/16/2016] [Indexed: 02/07/2023] Open
Abstract
In cells, positive strand RNA viruses, such as Retroviridae, must selectively recognize their full-length RNA genome among abundant cellular RNAs to assemble and release particles. How viruses coordinate the intracellular trafficking of both RNA and protein components to the assembly sites of infectious particles at the cell surface remains a long-standing question. The mechanisms ensuring packaging of genomic RNA are essential for viral infectivity. Since RNA packaging impacts on several essential functions of retroviral replication such as RNA dimerization, translation and recombination events, there are many studies that require the determination of RNA packaging efficiency and/or RNA packaging ability. Studies of RNA encapsidation rely upon techniques for the identification and quantification of RNA species packaged by the virus. This review focuses on the different approaches available to monitor RNA packaging: Northern blot analysis, ribonuclease protection assay and quantitative reverse transcriptase-coupled polymerase chain reaction as well as the most recent RNA imaging and sequencing technologies. Advantages, disadvantages and limitations of these approaches will be discussed in order to help the investigator to choose the most appropriate technique. Although the review was written with the prototypic simple murine leukemia virus (MLV) and complex human immunodeficiency virus type 1 (HIV-1) in mind, the techniques were described in order to benefit to a larger community.
Collapse
Affiliation(s)
- Mireia Ferrer
- CPBS, CNRS, Université de Montpellier, 1919 Route de Mende, Montpellier 34293, France.
| | - Simon Henriet
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen 5018, Norway.
| | - Célia Chamontin
- CPBS, CNRS, Université de Montpellier, 1919 Route de Mende, Montpellier 34293, France.
| | - Sébastien Lainé
- CPBS, CNRS, Université de Montpellier, 1919 Route de Mende, Montpellier 34293, France.
| | - Marylène Mougel
- CPBS, CNRS, Université de Montpellier, 1919 Route de Mende, Montpellier 34293, France.
| |
Collapse
|
26
|
Kalloush RM, Vivet-Boudou V, Ali LM, Mustafa F, Marquet R, Rizvi TA. Packaging of Mason-Pfizer monkey virus (MPMV) genomic RNA depends upon conserved long-range interactions (LRIs) between U5 and gag sequences. RNA (NEW YORK, N.Y.) 2016; 22:905-919. [PMID: 27095024 PMCID: PMC4878616 DOI: 10.1261/rna.055731.115] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 03/09/2016] [Indexed: 06/05/2023]
Abstract
MPMV has great potential for development as a vector for gene therapy. In this respect, precisely defining the sequences and structural motifs that are important for dimerization and packaging of its genomic RNA (gRNA) are of utmost importance. A distinguishing feature of the MPMV gRNA packaging signal is two phylogenetically conserved long-range interactions (LRIs) between U5 and gag complementary sequences, LRI-I and LRI-II. To test their biological significance in the MPMV life cycle, we introduced mutations into these structural motifs and tested their effects on MPMV gRNA packaging and propagation. Furthermore, we probed the structure of key mutants using SHAPE (selective 2'hydroxyl acylation analyzed by primer extension). Disrupting base-pairing of the LRIs affected gRNA packaging and propagation, demonstrating their significance to the MPMV life cycle. A double mutant restoring a heterologous LRI-I was fully functional, whereas a similar LRI-II mutant failed to restore gRNA packaging and propagation. These results demonstrate that while LRI-I acts at the structural level, maintaining base-pairing is not sufficient for LRI-II function. In addition, in vitro RNA dimerization assays indicated that the loss of RNA packaging in LRI mutants could not be attributed to the defects in dimerization. Our findings suggest that U5-gag LRIs play an important architectural role in maintaining the structure of the 5' region of the MPMV gRNA, expanding the crucial role of LRIs to the nonlentiviral group of retroviruses.
Collapse
Affiliation(s)
- Rawan M Kalloush
- Department of Microbiology and Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Valérie Vivet-Boudou
- Architecture et Réactivité de l'ARN, CNRS, IBMC, Université de Strasbourg, 67084 Strasbourg cedex, France
| | - Lizna M Ali
- Department of Microbiology and Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Farah Mustafa
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Roland Marquet
- Architecture et Réactivité de l'ARN, CNRS, IBMC, Université de Strasbourg, 67084 Strasbourg cedex, France
| | - Tahir A Rizvi
- Department of Microbiology and Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| |
Collapse
|
27
|
Cáceres CJ, Contreras N, Angulo J, Vera-Otarola J, Pino-Ajenjo C, Llorian M, Ameur M, Lisboa F, Pino K, Lowy F, Sargueil B, López-Lastra M. Polypyrimidine tract-binding protein binds to the 5' untranslated region of the mouse mammary tumor virus mRNA and stimulates cap-independent translation initiation. FEBS J 2016; 283:1880-901. [PMID: 26972759 DOI: 10.1111/febs.13708] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 03/01/2016] [Accepted: 03/08/2016] [Indexed: 12/23/2022]
Abstract
The 5' untranslated region (UTR) of the full-length mRNA of the mouse mammary tumor virus (MMTV) harbors an internal ribosomal entry site (IRES). In this study, we show that the polypyrimidine tract-binding protein (PTB), an RNA-binding protein with four RNA recognition motifs (RRMs), binds to the MMTV 5' UTR stimulating its IRES activity. There are three isoforms of PTB: PTB1, PTB2, and PTB4. Results show that PTB1 and PTB4, but not PTB2, stimulate MMTV-IRES activity. PTB1 promotes MMTV-IRES-mediated initiation more strongly than PTB4. When expressed in combination, PTB1 further enhanced PTB4 stimulation of the MMTV-IRES, while PTB2 fully abrogates PTB4-induced stimulation. PTB1-induced stimulation of MMTV-IRES was not altered in the presence of PTB4 or PTB2. Mutational analysis reveals that stimulation of MMTV-IRES activity is abrogated when PTB1 is mutated either in RRM1/RRM2 or RRM3/RRM4. In contrast, a PTB4 RRM1/RRM2 mutant has reduced effect over MMTV-IRES activity, while stimulation of the MMTV-IRES activity is still observed when the PTB4 RRM3/RMM4 mutant is used. Therefore, PTB1 and PTB4 differentially stimulate the IRES activity. In contrast, PTB2 acts as a negative modulator of PTB4-induced stimulation of MMTV-IRES. We conclude that PTB1 and PTB4 act as IRES trans-acting factors of the MMTV-IRES.
Collapse
Affiliation(s)
- Carlos J Cáceres
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Nataly Contreras
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Jenniffer Angulo
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Jorge Vera-Otarola
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Constanza Pino-Ajenjo
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | | | - Melissa Ameur
- Centre national de la Recherche Scientifique, Unité Mixte de Recherche 8015, Laboratoire de Cristallographie et RMN Biologique, Université Paris Descartes, France
| | - Francisco Lisboa
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Karla Pino
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Fernando Lowy
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Bruno Sargueil
- Centre national de la Recherche Scientifique, Unité Mixte de Recherche 8015, Laboratoire de Cristallographie et RMN Biologique, Université Paris Descartes, France
| | - Marcelo López-Lastra
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| |
Collapse
|