1. 9.11 Viruses That Use Reverse Transcriptase
Retroviruses (RNA viruses) and hepadnaviruses (DNA viruses) use reverse transcriptase for replication
Key first step in virus replication cycle
Reverse Transcriptase
Enzyme activity that converts ss RNA into ds DNA

2. 9.11 Viruses That Use Reverse Transcriptase
Retroviruses
Genome RNA reverse transcribed to dsDNA
Aka “cDNA” inserts into chromosome
Provirus
Gene expression and protein processing are complex (Figure 9.22)
Gag, pol, env gene regions common to all retroviruses
Retroviruses that cause cancer often have an extra gene region “src”

4. * Figure 9.22 Cap gag pol env AAAAA... GAG GAG - POL POL Capsid
Processing
of GAG
GAG
GAG - POL
Processing
of GAG-POL
POL
Capsid
proteins
Protease
Reverse
transcriptase
Integrase
Cap
env
Figure 9.22 Translation of retrovirus mRNA and processing of the proteins.
AAAAA...
Deleted
region
ENV
EP1
EP2
Figure 9.22

5. 9.11 Viruses That Use Reverse Transcriptase
Gag, pol, env regions common to all retroviruses
Retroviruses that cause cancer often have an extra gene region “src”
Host cell gene acquired by mistake
“v-src” is the name given to the gene

12. The retrovirus cDNA becomes a permanent part of the
host DNA
May impact genes near site of insertion-interruption,
transduction, or through LTR
Germ cell infection?

13. LTR = Long Terminal Repeat
Control region in viral genome
Usually an up-regulator
May impact downstream host genes
Can be transduced-then affect genes in new host cell

15. HERV =
Human
Endogenous
Retro-
Virus

16. Links to chronic disease? Genetic archeology?