Mechanism of Reverse Transcription

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 calledreverse 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.

1. A retrovirus-specific cellular tRNA hybridizes with a complementary region called the primer-binding site (PBS).
2. A DNA segment is extended from tRNA based on the sequence of the retroviral genomic RNA.
3. The viral R and U5 sequences are removed by RNase H.
4. First jump: DNA hybridizes with the remaining R sequence at the 3' end.
5. A DNA strand is extended from the 3' end.
6. Most viral RNA is removed by RNase H.
7. A second DNA strand is extended from the viral RNA.
8. Both tRNA and the remaining viral RNA are removed by RNase H.
9. Second jump: The PBS region of the second strand hybridizes with the PBS region of the first strand.
10. Extension on both DNA strands.  LTR stands for "long terminal repeat".