Related Experiment Video
Updated: Aug 14, 2026
11:19
Pairwise Growth Competition Assay for Determining the Replication Fitness of Human Immunodeficiency Viruses
Published on: May 4, 2015
Sequences in the 5' and 3' R elements of human immunodeficiency virus type 1 critical for efficient reverse
1Department of Microbiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA.
Journal of Virology
|August 23, 2000
Summary
Mutations in the HIV-1 R region near the U3-R junction disrupt reverse transcription by destabilizing cDNA. Mismatches within 10 nucleotides of this junction impair viral replication.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- The human immunodeficiency virus type 1 (HIV-1) genome features terminal repeat (R) sequences crucial for reverse transcription.
- These R regions are vital for first-strand transfer, a key step in synthesizing full-length viral cDNA.
Purpose of the Study:
- To investigate the role of specific mutations within the HIV-1 R sequences on reverse transcription efficiency.
- To determine the impact of mismatches in R regions on viral infectivity and DNA synthesis.
Main Methods:
- Introduction of mutations into the 5', 3', or both R sequences of HIV-1.
- Single-round infectivity assays and semiquantitative PCR analysis to assess reverse transcription.
- Endogenous reverse transcription assays using disrupted virus particles.
Main Results:
- Mutations within the first 10 nucleotides of the 5' or 3' R sequences significantly impaired reverse transcription in infected cells.
- Small mismatches (as little as 3 bp) near the U3-R junction caused inefficient reverse transcription.
- Identically mutated R elements in disrupted virions showed no intrinsic defect in DNA synthesis, suggesting a cell-dependent defect.
Conclusions:
- Mismatches within 10 nucleotides downstream of the U3-R junction in HIV-1 destabilize cDNA, leading to its disappearance during first-strand transfer.
- These findings suggest that first-strand transfer primarily occurs after the complete copying of the 5' R region.
- The precise location of R sequence mismatches is critical for HIV-1 reverse transcription and infectivity.
More Related Videos
12:03Evaluation of the Efficacy And Toxicity of RNAs Targeting HIV-1 Production for Use in Gene or Drug Therapy
Published on: September 5, 2016
13:07Determining 3'-Termini and Sequences of Nascent Single-Stranded Viral DNA Molecules during HIV-1 Reverse Transcription in Infected Cells
Published on: January 30, 2019
Related Concept Videos
01:10Retrovirus Life Cycles
Retroviruses have a single-stranded RNA genome that undergoes a special form of replication. Once the retrovirus has entered the host cell, an enzyme called reverse transcriptase synthesizes double-stranded DNA from the retroviral RNA genome. This DNA copy of the genome is then integrated into the host’s genome inside the nucleus via an enzyme called integrase. Consequently, the retroviral genome is transcribed into RNA whenever the host’s genome is transcribed, allowing the retrovirus to...
02:33Retroviruses
Retroviruses and retrotransposons both insert copies of their genetic elements into the genome of the host cell. Thus, the viral genes are passed on when the host genome is replicated or translated. A typical retroviral DNA sequence contains 3-4 genes that encode the different proteins required for its structural assembly and function as a molecular parasite. This DNA is transcribed into a single mRNA, which is very similar in structure to conventional mRNAs, i.e., it is capped at the 5’...
03:08LTR Retrotransposons
LTR retrotransposons are class I transposable elements with long terminal repeats flanking an internal coding region. These elements are less abundant in mammals compared to other class I transposable elements. About 8 percent of human genomic DNA comprises LTR retrotransposons. Some of the common examples of LTR retrotransposons are Ty elements in yeast and Copia elements in Drosophila.
The internal coding region of LTR retrotransposons and their mechanism of transposition closely resembles a...
The internal coding region of LTR retrotransposons and their mechanism of transposition closely resembles a...
01:26Size and Structure of Viral Genomes
Viral genomes exhibit remarkable diversity in size, structure, and composition, influencing their replication strategies and interactions with host cells. These genomes consist of either DNA or RNA and may be linear or circular. Additionally, they can be single-stranded or double-stranded, with each configuration affecting how the virus propagates within a host. RNA viruses, for instance, generally have smaller genomes than DNA viruses, a factor that contributes to their high mutation rates and...
01:29Viruses with RNA Genomes
RNA viruses are categorized into positive-strand, negative-strand, or double-stranded groups based on their genomic structure and replication mechanisms. This classification dictates how they exploit host cellular machinery for protein synthesis and replication. Some RNA viruses also utilize reverse transcription as part of their life cycle, further diversifying their replication strategies.Positive-Strand RNA VirusesPositive-strand RNA viruses have genomes that function directly as messenger...
01:19Inhibitors of Virion Maturation and Assembly
As part of their replication cycle, certain viruses synthesize long precursor proteins called polyproteins within infected host cells. In human immunodeficiency virus (HIV), two major polyproteins are produced: Gag and Gag-Pol. The Gag polyprotein supplies the structural components of the virus, while Gag-Pol includes essential viral enzymes such as reverse transcriptase, integrase, and protease. After synthesis, these polyproteins move to the host cell membrane, where they assemble into an...