scholarly journals Complementarity-directed RNA dimer-linkage promotes retroviral recombination in vivo

2004 ◽  
Vol 32 (1) ◽  
pp. 102-114 ◽  
Author(s):  
J. G. Mikkelsen
Keyword(s):  
Rna Dimer ◽  
Dimer Linkage ◽  
Retroviral Recombination

scholarly journals Effect of the Murine Leukemia Virus Extended Packaging Signal on the Rates and Locations of Retroviral Recombination

2000 ◽  
Vol 74 (15) ◽  
pp. 6953-6963 ◽  
Author(s):  
Jeffrey A. Anderson ◽  
Vinay K. Pathak ◽  
Wei-Shau Hu
Keyword(s):  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Template Switching ◽  
Packaging Signal ◽  
Lower Efficiency ◽  
Selectable Markers ◽  
Negative Interference ◽  
Dimer Linkage ◽  
Retroviral Recombination ◽  
Murine Leukemia

ABSTRACT Reverse transcriptase (RT) switches templates frequently during DNA synthesis; the acceptor template can be the same RNA (intramolecular) or the copackaged RNA (intermolecular). Previous results indicated that intramolecular template switching occurred far more frequently than intermolecular template switching. We hypothesized that intermolecular template-switching events (recombination) occurred at a lower efficiency because the copackaged RNA was not accessible to the RT. To test our hypothesis, the murine leukemia virus (MLV) extended packaging signal (Ψ+) containing a dimer linkage structure (DLS) was relocated from the 5′ untranslated region (UTR) to between selectable markers, allowing the two viral RNAs to interact closely in this region. It was found that the overall maximum recombination rates of vectors with Ψ+ in the 5′ UTR or Ψ+ between selectable markers were not drastically different. However, vectors with Ψ+ located between selectable markers reached a plateau of recombination rate at a shorter distance. This suggested a limited enhancement of recombination by Ψ+. The locations of the recombination events were also examined by using restriction enzyme markers. Recombination occurred in all four regions between the selectable markers; the region containing 5′ Ψ+ including DLS did not undergo more recombination than expected from the size of the region. These experiments indicated that although the accessibility of the copackaged RNA was important in recombination, other factors existed to limit the number of viruses that were capable of undergoing intermolecular template switching. In addition, recombinants with multiple template switches were observed at a frequency much higher than expected, indicating the presence of high negative interference in the MLV-based system. This extends our observation with the spleen necrosis virus system and suggests that high negative interference may be a common phenomenon in retroviral recombination.

scholarly journals Mutations of the Kissing-Loop Dimerization Sequence Influence the Site Specificity of Murine Leukemia Virus Recombination In Vivo

2000 ◽  
Vol 74 (2) ◽  
pp. 600-610 ◽  
Author(s):  
Jacob Giehm Mikkelsen ◽  
Anders H. Lund ◽  
Mogens Duch ◽  
Finn Skou Pedersen
Keyword(s):  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Single Point Mutation ◽  
Template Switching ◽  
Site Specificity ◽  
Rna Dimer ◽  
Rna Interaction ◽  
Murine Leukemia ◽  
Kissing Loop

ABSTRACT The genetic information of retroviruses is retained within a dimeric RNA genome held together by intermolecular RNA-RNA interactions near the 5′ ends. Coencapsidation of retrovirus-derived RNA molecules allows frequent template switching of the virus-encoded reverse transcriptase during DNA synthesis in newly infected cells. We have previously shown that template shifts within the 5′ leader of murine leukemia viruses occur preferentially within the kissing stem-loop motif, a cis element crucial for in vitro RNA dimer formation. By use of a forced recombination approach based on single-cycle transfer of Akv murine leukemia virus-based vectors harboring defective primer binding site sequences, we now report that modifications of the kissing-loop structure, ranging from a deletion of the entire sequence to introduction of a single point mutation in the loop motif, significantly disturb site specificity of recombination within the highly structured 5′ leader region. In addition, we find that an intact kissing-loop sequence favors optimal RNA encapsidation and vector transduction. Our data are consistent with the kissing-loop dimerization model and suggest that a direct intermolecular RNA-RNA interaction, here mediated by palindromic loop sequences within the mature genomic RNA dimer, facilitates hotspot template switching during retroviral cDNA synthesis in vivo.

Strand transfer to the 5′ part of a tRNA as a mechanism for retrovirus patch-repair recombination in vivo

2004 ◽  
Vol 85 (7) ◽  
pp. 1965-1969 ◽  
Author(s):  
María L. Carrasco ◽  
Mogens Duch ◽  
Finn Skou Pedersen
Keyword(s):  
Reverse Transcriptase ◽  
Transfer Mechanism ◽  
Patch Repair ◽  
Deletion Mutants ◽  
Strand Transfer ◽  
Leukaemia Virus ◽  
Trna Sequence ◽  
Strand Orientation ◽  
Retroviral Recombination

By screening for marker-cassette deletion mutants of a murine leukaemia virus-based replication-competent vector, two occurrences of tRNA sequence patch insertions were identified. In one of the cases, 28 nucleotides from the 5′ end of tRNALys4 were inserted in the plus-strand orientation, which points to a novel strand-transfer mechanism to tRNAs during reverse transcriptase-mediated retroviral recombination.

scholarly journals Retroviral RNA dimer linkage.

1998 ◽  
Vol 79 (12) ◽  
pp. 2877-2882 ◽  
Author(s):  
J Greatorex ◽  
A Lever
Keyword(s):  
Rna Dimer ◽  
Dimer Linkage

scholarly journals Retroviral Recombination In Vivo: Viral Replication Patterns and Genetic Structure of Simian Immunodeficiency Virus (SIV) Populations in Rhesus Macaques after Simultaneous or Sequential Intravaginal Inoculation with SIVmac239Δvpx/Δvpr and SIVmac239Δnef

2005 ◽  
Vol 79 (8) ◽  
pp. 4886-4895 ◽  
Author(s):  
Eun-Young Kim ◽  
Marc Busch ◽  
Kristina Abel ◽  
Linda Fritts ◽  
Patty Bustamante ◽  
...  
Keyword(s):  
Simian Immunodeficiency Virus ◽  
Rhesus Macaques ◽  
Viral Fitness ◽  
Compensatory Mutation ◽  
Wild Type ◽  
Lower Plasma ◽  
Immunodeficiency Virus ◽  
Retroviral Recombination ◽  
Kinetics Of

ABSTRACT To characterize the occurrence, frequency, and kinetics of retroviral recombination in vivo, we intravaginally inoculated rhesus macaques, either simultaneously or sequentially, with attenuated simian immunodeficiency virus (SIV) strains having complementary deletions in their accessory genes and various degrees of replication impairment. In monkeys inoculated simultaneously with SIVmac239Δvpx/Δvpr and SIVmac239Δnef, recombinant wild-type (wt) virus and wild-type levels of plasma viral RNA (vRNA) were detected in blood by 2 weeks postinoculation. In monkeys inoculated first with SIVmac239Δvpx/Δvpr and then with SIVmac239Δnef, recombination occurred but was associated with lower plasma vRNA levels than plasma vRNA levels seen for monkeys inoculated intravaginally with wt SIVmac239. In one monkey, recombination occurred 6 weeks after the challenge with SIVmac239Δnef when plasma SIVmac239Δvpx/Δvpr RNA levels were undetectable. In monkeys inoculated first with the more highly replicating strain, SIVmac239Δnef, and then with SIVmac239Δvpx/Δvpr, wild-type recombinant virus was not detected in blood or tissues. Instead, a virus that had repaired the deletion in the nef gene by a compensatory mutation was found in one animal. Overall, recombinant SIV was eventually found in four of six animals intravaginally inoculated with the two SIVmac239 deletion mutants. These findings show that recombination can occur readily in vivo after mucosal SIV exposure and thus contributes to the generation of viral genetic diversity and enhancement of viral fitness.

Fine Structural Changes in the Microvasculature of the Mouse Pinna: Aging and Radiation Injury

1974 ◽  
Vol 32 ◽  
pp. 54-55
Author(s):  
S. Phyllis Steamer ◽  
Rosemarie L. Devine
Keyword(s):  
Structural Changes ◽  
Radiation Treatment ◽  
Arterial Stenosis ◽  
Ultrastructural Changes ◽  
Vascular Effects ◽  
Microvascular Changes ◽  
Surrounding Connective Tissue ◽  
Fission Neutrons ◽  
Total Body

The importance of radiation damage to the skin and its vasculature was recognized by the early radiologists. In more recent studies, vascular effects were shown to involve the endothelium as well as the surrounding connective tissue. Microvascular changes in the mouse pinna were studied in vivo and recorded photographically over a period of 12-18 months. Radiation treatment at 110 days of age was total body exposure to either 240 rad fission neutrons or 855 rad 60Co gamma rays. After in vivo observations in control and irradiated mice, animals were sacrificed for examination of changes in vascular fine structure. Vessels were selected from regions of specific interest that had been identified on photomicrographs. Prominent ultrastructural changes can be attributed to aging as well as to radiation treatment. Of principal concern were determinations of ultrastructural changes associated with venous dilatations, segmental arterial stenosis and tortuosities of both veins and arteries, effects that had been identified on the basis of light microscopic observations. Tortuosities and irregularly dilated vein segments were related to both aging and radiation changes but arterial stenosis was observed only in irradiated animals.

Induction and Differentiation of Dental Epithelium in Vivo and in Vitro

1982 ◽  
Vol 40 ◽  
pp. 142-145
Author(s):  
E. J. Kollar
Keyword(s):  
Connective Tissue ◽  
Oral Mucosa ◽  
Basal Lamina ◽  
Functional Derivatives ◽  
Specific Source ◽  
Dental Epithelium ◽  
Connective Tissue Stroma

The differentiation and maintenance of many specialized epithelial structures are dependent on the underlying connective tissue stroma and on an intact basal lamina. These requirements are especially stringent in the development and maintenance of the skin and oral mucosa. The keratinization patterns of thin or thick cornified layers as well as the appearance of specialized functional derivatives such as hair and teeth can be correlated with the specific source of stroma which supports these differentiated expressions.

Ultrastructural Correlations between Clonal Human Tumor Colonies and in Vivo Neoplasms

1982 ◽  
Vol 40 ◽  
pp. 210-211
Author(s):  
M.J. Murphy ◽  
R.R. Price ◽  
J.C. Sloman
Keyword(s):  
Cultured Cells ◽  
Human Tumor ◽  
Cell Type ◽  
Tumor Mass ◽  
Initial Cell ◽  
Cloning Assay ◽  
Human Tumor Cloning ◽  
The Relationship

The in vitro human tumor cloning assay originally described by Salmon and Hamburger has been applied recently to the investigation of differential anti-tumor drug sensitivities over a broad range of human neoplasms. A major problem in the acceptance of this technique has been the question of the relationship between the cultured cells and the original patient tumor, i.e., whether the colonies that develop derive from the neoplasm or from some other cell type within the initial cell population. A study of the ultrastructural morphology of the cultured cells vs. patient tumor has therefore been undertaken to resolve this question. Direct correlation was assured by division of a common tumor mass at surgical resection, one biopsy being fixed for TEM studies, the second being rapidly transported to the laboratory for culture.

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