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Dzhivhuho G, Holsey J, Honeycutt E, O'Farrell H, Rekosh D, Hammarskjold ML, Jackson PEH. HIV-1 Rev-RRE functional activity in primary isolates is highly dependent on minimal context-dependent changes in Rev. Sci Rep 2022; 12:18416. [PMID: 36319640 PMCID: PMC9626594 DOI: 10.1038/s41598-022-21714-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 09/30/2022] [Indexed: 01/01/2023] Open
Abstract
During HIV infection, intron-containing viral mRNAs are exported from the cell nucleus to the cytoplasm to complete the replication cycle. Cellular restrictions on the export of incompletely spliced transcripts are overcome by a viral protein, Rev, and an RNA structure found in all unspliced and incompletely spliced viral mRNAs, the Rev Response Element (RRE). Primary HIV isolates display substantial variation in the sequence and functional activity of Rev proteins. We analyzed Rev from two primary isolates with disparate activity that resulted in differences in in vitro fitness of replication-competent viral constructs. The results showed that amino acid differences within the oligomerization domain, but not the arginine-rich motif or the nuclear export signal, determined the level of Rev activity. Two specific amino acid substitutions were sufficient to alter the low-activity Rev to a high-activity phenotype. Other mutations in Rev sequences had unpredictable effects on activity that differed between the two Rev backbones. The sensitivity of Rev function level to small sequence changes likely permits modulation of Rev-RRE activity during HIV infection, which may play a role in pathogenesis. The functional consequences of Rev mutations differed between primary isolates, highlighting the challenge of generalizing studies of Rev conducted using laboratory HIV strains.
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Affiliation(s)
- Godfrey Dzhivhuho
- Myles H. Thaler Center for HIV and Human Retrovirus Research, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, School of Medicine, University of Virginia, Charlottesville, VA, USA
| | - Jordan Holsey
- Myles H. Thaler Center for HIV and Human Retrovirus Research, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, School of Medicine, University of Virginia, Charlottesville, VA, USA
| | - Ethan Honeycutt
- Myles H. Thaler Center for HIV and Human Retrovirus Research, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, School of Medicine, University of Virginia, Charlottesville, VA, USA
| | - Heather O'Farrell
- Myles H. Thaler Center for HIV and Human Retrovirus Research, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, School of Medicine, University of Virginia, Charlottesville, VA, USA
| | - David Rekosh
- Myles H. Thaler Center for HIV and Human Retrovirus Research, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, School of Medicine, University of Virginia, Charlottesville, VA, USA
| | - Marie-Louise Hammarskjold
- Myles H. Thaler Center for HIV and Human Retrovirus Research, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, School of Medicine, University of Virginia, Charlottesville, VA, USA
| | - Patrick E H Jackson
- Myles H. Thaler Center for HIV and Human Retrovirus Research, University of Virginia, Charlottesville, VA, USA.
- Division of Infectious Diseases and International Health, School of Medicine, University of Virginia, Charlottesville, VA, USA.
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Watanabe CT, Rosenblatt JD, Bakker A, Morgan JP, Luo J, Chun S, Black AC. Negative regulation of gene expression from the HTLV type II long terminal repeat by Rex: functional and structural dissociation from positive posttranscriptional regulation. AIDS Res Hum Retroviruses 1996; 12:535-46. [PMID: 8679309 DOI: 10.1089/aid.1996.12.535] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Regulation of human T cell leukemia virus type II (HTLV-II) gene expression by Rex is mediated by cis-acting elements in the 5' viral long terminal repeat (LTR). Rex acts posttranscriptionally to enhance cytoplasmic accumulation of incompletely spliced viral mRNAs encoding structural proteins. We report a distinct negative regulatory function mediated by Rex affecting expression from the viral 5' LTR. Using both LTR-driven CAT reporters and a full-length HTLV-II proviral construct, we demonstrate that Rex decreases total cellular levels of LTR-containing mRNA in a dose-dependent manner. Negative regulation is an independent function as demonstrated by structural and functional dissociation from Rex positive posttranscriptional regulation. This negative regulatory action was dependent on nuclear localization sequences, but did not require the previously defined Rex-responsive element (RxRE). Negative regulation was observed in T cell lines but not in B cell lines, suggesting the involvement of cell type-specific factors distinct from those involved in posttranscriptional regulation. An internal deletion mutant of Rex removing aa 38-80 retained the ability to repress, but did not posttranscriptionally increase expression, while negative regulation requires a previously uncharacterized carboxy-terminal region (aa 154-170). These findings suggest that Rex may serve two simultaneous functions: to decrease overall levels of transcribed viral mRNA, and to facilitate nuclear to cytoplasmic export of mRNAs encoding structural proteins. The negative regulatory function of Rex may play a role in viral latency.
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Affiliation(s)
- C T Watanabe
- Department of Medicine, UCLA School of Medicine, Los Angeles, California, USA
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Tiley LS, Brown PH, Cullen BR. Does the human immunodeficiency virus Tat trans-activator contain a discrete activation domain? Virology 1990; 178:560-7. [PMID: 2219707 DOI: 10.1016/0042-6822(90)90354-t] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Human immunodeficiency virus type 1 (HIV-1) encodes a transcriptional trans-activator, termed Tat, that is absolutely required for viral replication in vitro. By analogy to other known transcription factors, it has been suggested that the HIV-1 Tat protein may contain discrete protein domains that determine sequence specificity and transcriptional activation potential. Here, we report the use of site-directed mutagenesis to examine the functional significance of two candidate activation domains within Tat. A 12 amino acid sequence adjacent to the N-terminus of the Tat protein, which includes a proposed acidic amphipathic alpha-helix activation motif, was found to contribute to, but be dispensable for, Tat function in vivo. In contrast, the integrity of a second potential Tat activation motif, centered on a lysine residue at position 41, was found to be essential for Tat function. However, Tat proteins mutated in this area displayed a fully recessive negative phenotype. Therefore, neither of these two regions of the Tat protein appear to be discrete activation domains. We conclude that previous attempts to categorize Tat as a modular transcription factor have not succeeded and suggest that the functional organization of this complex trans-activator remains to be defined.
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Affiliation(s)
- L S Tiley
- Department of Microbiology and Immunology, Duke University Medical Center, Durham, North Carolina 27710
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