Intro to retroviruses Flashcards
What are the key steps in the HIV replication cycle?
Virus Binding → Membrane Fusion
Reverse Transcription: ssRNA → dsDNA
Nuclear Transport & Integration
Transcription & Translation
Assembly & Budding via plasma membrane/MVB
Maturation
What is TRIM5α?
A tripartite motif-containing protein that blocks HIV-1 replication in non-human primates.
Mechanism: Binds HIV capsid → disrupts it. Induces ubiquitinylation & proteasomal degradation. Prevents reverse transcription.
How does TRIM5α exhibit species specificity?
Rhesus/African green monkey TRIM5α restricts HIV-1, while human TRIM5α is ineffective due to SPRY domain mutations.
What is APOBEC3G?
An apolipoprotein B mRNA editing enzyme that causes C → U mutations in viral DNA.
Incorporated into virions unless countered by Vif.
What is the function of Vif?
Counteracts APOBEC3G by ubiquitinating and degrading it via the proteasomal pathway.
What is Tetherin?
A protein that blocks the viral release of enveloped viruses (e.g., HIV, Ebola).
Mechanism: Tethers virions to the plasma membrane, preventing release.
How does HIV counteract Tetherin?
HIV Vpu degrades tetherin, allowing viral release.
What is SAMHD1?
A protein expressed in myeloid cells that depletes dNTP pools, preventing reverse transcription.
How does HIV-2 counteract SAMHD1?
HIV-2 Vpx degrades SAMHD1, allowing viral replication.
What are SERINC3/5?
Serine incorporator proteins that inhibit HIV infectivity by blocking viral fusion.
How does HIV counteract SERINC3/5?
The Nef protein removes SERINC3/5 from virions, ensuring infectivity.
What is NONO?
A nuclear sensor for retroviral DNA that links HIV detection to the cGAS pathway.
What is Fv1?
A protein found in mice that restricts Murine Leukemia Virus (MLV).
Mechanism: Binds capsid and blocks infection.
What are key research methods for studying restriction factors?
TRIM5α identification through cDNA libraries, cell fusion experiments, and GFP-negative selection via FACS. Reverse genetics to study Vif and Vpu mutants.
What is the summary of retroviral restriction factors?
They are key innate immune defenses against HIV, blocking different stages of HIV replication and limiting viral spread.
