53 Questions
During which step is the RNase H enzyme involved in the process?
Step 2: Removal of template RNA
What is the function of the polypurine tract (ppt) in the process?
Acts as a primer for synthesis of +strand DNA by RT
What is the role of the primer binding site (PBS) in the process?
Exposes primer binding site on +strand DNA after removal of tRNA and ppt primer
Which step results in the production of long-terminal repeat (LRT) with ends bearing U3-R-U5’?
Step 6: Synthesis of plus-strand strong-stop DNA
What is the role of reverse transcriptase (RT) in the process of retroviral replication?
It synthesizes a linear dsDNA with LTRs on both ends called proviral DNA
What is the function of integrase (IN) in retroviral replication?
It brings together the two ends of proviral DNA and facilitates its integration into the host genome
What happens during the late phase of retroviral replication?
Viral RNA and protein synthesis occur, and virions mature into infectious particles after budding from the plasma membrane
What is the role of U3 in retroviral replication?
U3 contains specific sequences that interact with cellular machinery to control transcription conditions
What happens during virion maturation in retroviral replication?
Env protein is translocated into the lumen of ER, then through Golgi, and directed to plasma membrane
What is a quasispecies in retroviral replication?
A collection of variants due to small mutations
What is required for integration of proviral DNA into the host genome?
The presence of integrase that brings together two ends of proviral DNA and facilitates integration into host genome
What are the functions of U3 in retroviral replication?
It contains specific sequences that interact with cellular machinery to control transcription conditions
How does repair synthesis occur after integration of proviral DNA into the host genome?
Host enzymes carry out repair synthesis of gaps in the host DNA after integration
During which step in retroviral replication is the RNase H enzyme involved?
Removal of template RNA
What is the function of the long-terminal repeat (LRT) produced during retroviral replication?
Acts as a primer for synthesis of +strand DNA by RT
What occurs during the second strand transfer in retroviral replication?
Exposed PBS can hybridize with PBS’
What is the role of the polypurine tract (ppt) in retroviral replication?
Acts as a primer for synthesis of +strand DNA by RT
What is the role of the primer binding site (PBS) in retroviral replication?
Initiates the synthesis of plus-strand strong-stop DNA
During which step is the RNase H enzyme involved in retroviral replication?
Removal of template RNA
What happens during the second strand transfer in retroviral replication?
Exposed PBS hybridizes with PBS'
What is the function of U3 in retroviral replication?
Provides promoter and enhancer sequences for transcription
During retroviral replication, what is the function of the primer binding site (PBS) on the plus-strand DNA?
It acts as a primer for synthesis of plus-strand DNA by RT
What occurs during the first-strand transfer in retroviral replication?
Extended DNA copy of R+U5’ transfers from 5’ end to 3’ end of genome RNA
What is the role of the polypurine tract (ppt) in retroviral replication?
Acts as a primer for synthesis of plus-strand DNA by RT
What happens during the removal of template RNA in retroviral replication?
RNase H digests RNA in DNA:RNA hybrid
What is the role of the primer binding site (PBS) in retroviral replication?
It serves as the binding site for tRNA primer for initiation of reverse transcription
What is a quasispecies in retroviral replication?
A collection of variants due to small mutations within the retroviral population
What occurs during the second strand transfer in retroviral replication?
The newly synthesized viral DNA strand is integrated into the host genome
What happens during virion maturation in retroviral replication?
Protease is activated and cleaves Gag/Pol into mature single proteins after assembly
What is required for integration of proviral DNA into the host genome?
Integrase (IN) bringing together two ends of proviral DNA
What is the function of U3 in retroviral replication?
Controls under what conditions transcription takes place
During which step is the RNase H enzyme involved in retroviral replication?
During second strand transfer, removing RNA from newly synthesized viral DNA strand
What is required for repair synthesis after integration of proviral DNA into the host genome?
Host enzymes carry out repair synthesis of gaps in integrated viral DNA
What happens during late phase of replication in retroviral replication?
Viral RNA and protein synthesis, assembly of virions occur
What occurs during infection with progeny virus in spread of infection?
Infection with new virus particles produced from existing infected cells contributes to spread
Which protein is responsible for directing the transport of proviral DNA into the cell nucleus during HIV-1 infection?
Vpr
What is the primary receptor found on both T lymphocytes and monocytes/macrophages targeted by HIV-1?
CD4
Which step in HIV-1 replication involves the exposure of gp41 (fusion domain) to insert in the host cell membrane?
Fusion with host cell membranes
What occurs after close proximity of viral and host cell membranes during HIV-1 infection?
Fusion with host cell membranes
What is the role of reverse transcriptase (RT) in HIV-1 replication?
Replicates viral genome but generates small mutations
What determines co-receptor usage in HIV-1 infection?
Variations in viral SU (gp120)
Which protein interacts directly with nuclear components to direct transport into the nucleus during HIV-1 infection?
Vpr
What is the function of capsid protein MA during HIV-1 infection?
Directs transport of proviral DNA into the cell nucleus
Which viral protein supports elongation of HIV-1 transcription by binding to TAR?
Rev
What is the function of Vpu in HIV-1 replication?
Enhances release of progeny virions from infected cells and induces degradation of tetherin
What is the role of Nef in HIV-1 infection?
Decreases surface expression of CD4 and MHC1, modifying cell signaling in T cells
Which protein continuously shuttles between cytoplasm and nucleus during HIV-1 replication?
Rev
What is the function of Vif in HIV-1 replication?
Increases virion infectivity by counteracting host cell antiviral factors such as APOBEC3G
What is the function of Vpr in HIV-1 replication?
Can arrest infected cells in G2 stage of cell cycle
Which step initiates assembly and budding of HIV-1 during replication?
Genome packaging signal (psi) on genomic RNA
Which viral protein is essential for transport of mRNAs encoding structural proteins?
Rev
What is the effect of Tat on RNA polymerase during HIV-1 transcription?
Recruits cellular Cdk9 and Cyclin T to enhance processivity
What is the regulation mechanism for latent infection involving HIC-1 LTRs?
Sensitive to various cellular stimuli
Study Notes
HIV-1 Molecular Mechanisms and Protein Functions
- HIV-1 cure is complicated by host genome integration and immune system inability to identify infected cells without viral protein expression
- Latent infection regulation involves transcriptional control elements in HIC-1 LTRs, sensitive to various cellular stimuli
- Patients with latent HIV-1 infection must continue treatment for life
- The viral Tat protein, localized in the nucleus, supports elongation of HIV-1 transcription by binding to TAR
- In absence of Tat, RNA polymerase lacks processivity, and in its presence, cellular Cdk9 and Cyclin T are recruited to enhance processivity
- Rev mediates cytoplasmic transport of viral mRNAs encoding HIV-1 structural proteins and continuously shuttles between cytoplasm and nucleus
- Tat and Rev are essential for HIV transcription and transport of mRNAs encoding structural proteins
- Vif increases virion infectivity by counteracting host cell antiviral factors such as APOBEC3G
- Vpr enhances HIV-1 replication and can arrest infected cells in G2 stage of cell cycle
- Vpu enhances release of progeny virions from infected cells and induces degradation of tetherin, a host antiviral protein
- Nef decreases surface expression of CD4 and MHC1, modifying cell signaling in T cells and affecting the immune response
- Genome packaging signal (psi) on genomic RNA initiates assembly and budding of HIV-1, with protease activation cleaving Gag and Gag-Pol polyproteins into individual peptides for infection
Test your knowledge on the steps involved in HIV reverse transcription, including the synthesis of minus strand strong-stop DNA, removal of template RNA, first-strand transfer, and copying of the full-length genome. This quiz will challenge your understanding of the intricate process of HIV replication.
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