After the RNA retrovirus enters a host cell, its genomic RNA will be
transcribed into a double stranded DNA and then integrated into the host
DNA. The RNA to DNA transcription is called reverse transcription.
Figure 4-J-1. Mechanism of reverse
transcription. The entire process is catalyzed by reverse transcriptase
which has both DNA polymerase and RNase H activities.
- A retrovirus-specific cellular tRNA hybridizes with a complementary region
called the primer-binding site (PBS).
- A DNA segment is extended from tRNA based on the sequence of the
retroviral genomic RNA.
- The viral R and U5 sequences are removed by RNase H.
- First jump: DNA hybridizes with the remaining R sequence at the 3' end.
- A DNA strand is extended from the 3' end.
- Most viral RNA is removed by RNase H.
- A second DNA strand is extended from the viral RNA.
- Both tRNA and the remaining viral RNA are removed by RNase H.
- Second jump: The PBS region of the second strand hybridizes with the PBS
region of the first strand.
- Extension on both DNA strands. LTR
stands for "long terminal repeat".