1. Plate 36
Retroviruses

2. Reverse transcriptase
Retrovirus Structure
All retroviruses:
Are surrounded by a viral envelope
Are icosahedral in shape
Contain 2 identical molecules of RNA
Contain the enzyme reverse transcriptase
Viral RNA
Reverse transcriptase
Glycoproteins
Lipids
Envelope

3. DNA Viruses vs. Retroviruses
“Retro” means “backwards”
DNA viruses undergo transcription and translation:
DNA  RNA  viral proteins
Retroviruses undergo reverse transcription and translation:
RNA  DNA  RNA  viral proteins
Reverse transcriptase allows the single-stranded RNA to be transcribed into double-stranded DNA

4. Infection
Glycoproteins on the viral envelope allow the virus to attach to the receptor sites of the host cell
The virus then fuses with the cell membrane of the host

5. Reverse Transcription
Once a virus has penetrated the cell membrane, the RNA undergoes reverse transcription in the cytoplasm: RNA  DNA
The viral DNA then gets integrated into the host cell’s chromosomal DNA (viral DNA now known as a provirus)
The viral DNA is then passively replicated

6. Latency
Retroviral DNA can remain dormant in the host cell’s chromosomal DNA for a long period of time (latency – from Latin word for “hidden”)
This is part of the lysogenic cycle

7. http://highered. mcgraw-hill

9. Retrovirus Diseases
Retrovirus infections can lead to HIV/AIDS, cancer, and tumors
Reverse-transcriptase inhibitors prevent viruses from converting their RNA into DNA, thus rendering them inactive
HIV virus

10. Fun Facts!
It is believed that almost 8% of human DNA comes from retroviruses, most of which is considered “junk DNA”
During reverse transcription, mutations are common which allows retroviruses to become resistant to antiviral drugs
Viral DNA may trigger cancer and tumor growth by being randomly integrated into a oncogene